/\ Um >v<^ ' ^\ \T/ v v\ TUF y% ^ mil rat. . r ^% ^ t 7 / PRACTICAL DISSECTIONS. ✓ PRACTICAL DISSECTIONS BY RICHARD M. HODGES, M. D DEMONSTRATOR OF ANATOMY IN THE MEDICAL DEPARTMENT OF HARVARD UNIVERSITY. 919Z CAMBRIDGE: JOHN BARTLETT, BOOKSELLER TO THE UNIVERSITY. M DCCC Lvm. as HI/* S - i 7. a$ Entered according to Act of Congress, in the year 1858, by John Bartlett, in the Clerk's Office of the District Court of the District of Massachusetts RIVERSIDE, CAMBRIDGE: PRINTED BY H. 0. HOCGHTON AND COMPANY PREFACE. The " Practical Dissections " is not a Treatise on Anatomy, nor in any way a substitute for one. It is intended to be simply a practical guide in the or- dinary dissections of the Medical Student, describ- ing on the same page^and in connection, the muscles, nerves, arteries, veins or other structures which are conjointly exposed, and only so far as exposed, in dissecting any one of the parts into which the dead subject is usually divided. Remembering that " the smallness of the size of a book is always its own recommendation, as on the contrary, the largeness of a book is its own disadvantage, as well as the terror of learning," all Minute Anatomy, and the de- tails of arterial distribution, beyond what an ordinary injection exhibits, or of nervous ramifications which only special dissections can demonstrate, h#ve pur- posely been omitted, or, if introduced, as has been done almost of necessity in a few places, are ac- companied by the statement that their verification in an ordinary dissection is not to be expected. The order observed in the following pages is an entirely arbitrary one, but which an experience of seven years in demonstrating, and more than ten in VI PREFACE. the special study of Anatomy, has shown to be the most convenient in the Dissecting Room, and the most economical of material. The division of the descriptions into " dissections," each intended to comprise a day's work, it is believed will be found advantageous, not only as mapping out the labor before the Dissector, but in giving him an opportu- nity to prepare in the study, and in advance, for the dissection of each succeeding day. Practical sug- gestions, and the best method of demonstrating, precede the descriptions of the various regions and parts of regions. Illustrations have been omitted, for the reason that they add to the expense of a book, often without enhancing its real value, and from a belief that they are liable to great abuse, by distracting attention from the descriptive text to the numbered references, the simple verification of the latter taking the place of the full information only to be obtained from the former. Boston, Nov. 1858. CONTENTS. General Rules to be observed in Dissecting......................... xi PART FIRST. ANATOMY OF THE HEAD AND NECK. DISSECTION PAGE I. External Ear.............................................. 1 Frontal and Orbital Region................................. 3 II. Facial Region............................................. 6 Facial Arteries............................................ 10 Facial Nerves............................................. 1° Parotid Gland and Region.................................. 11 DX Dura Mater and Sinuses.................................... 13 Arteries and Muscles of the Orbit........................... 18 IV. Cranial Nerves at their Exit from the Skull................. 20 V. Superficial Cervical Region................................. 25 VI. External Carotid Artery.................................... 30 Submaxillary Region....................................... 32 VII. Pterygo-maxillary Region.................................. 34 VIII. Sterno-clavicular Articulation.............................. 40 Base of the Neck.......................................... 40 IX. Articulation of the Lower Jaw.............................. 46 Pharynx.................................................. 46 Palatine Region........................................... 48 Otic and Meckel's Ganglia.................................. 49 Nasal Fossae...............................•............... 51 X. Tongue................................................... 61 Larynx................................................... 53 XI. Prevertebral Region........................................ 57 Ligaments of the first two Vertebrae......................... 59 XII. Anatomy of the Eye....................................... 60 XIII. Membranes, and Vessels of the Encephalon.................. 64 Origins of the Cranial Nerves............................... 67 Medulla Oblongata and Pons Varolii......................... 68 vm CONTENTS. DISSECTION PAGE XIII. Base of the Cerebrum...................................... 69 Upper surface and Interior of the Cerebrum.................. 70 Cerebellum............................................... 76 XIV. The Internal Auditory Apparatus........................... 78 Middle Ear...................'............................. 79 Internal Ear............................................... 81 PART SECOND. ANATOMY OF THE UPPER EXTREMITY, THORAX, AND BACK. I. Pectoral and Deltoid Region................................ 85 Axilla.................................................... 87 II. Front of the Arm.......................................... 89 Bend of the Elbow......................................... 93 HI. Sternal Region............................................ 95 Anterior Mediastinum...................................... 96 Heart.................................................... 99 IV. Posterior Mediastinum..................................... 103 Lungs.................................................... 108 V. The Back and Posterior Cervical Region.................... 109 Spinal Cord and Membranes................................ 117 VI. Scapular Region........................................... 121 Back of the Arm.......................................... 123 VII. Front of the Fore-arm..............................„...... 124 VIII. Back of the Fore-arm and Hand............................. 129 IX. Palm of the Hand......................................... 134 X. Ligaments of the Sternum, Ribs, Spine, and Upper Extremity. 140 PART THIRD. ANATOMY OF THE ABDOMEN AND LOWER EXTREMITY. I. Parietes of the Abdomen................................... 146 Anatomy of Inguinal Hernia................................ 152 II. Visceral Cavity.................................... 155 Peritoneum.................................... i57 Ducts, Vessels, and Nerves of the Abdominal Cavity.......... 159 III. Intestinal Tube......................... 16fi The Spleen.............................. _ . .. eq The Pancreas.......... ,..,, _, T. ........................................ 1*0 The Liver.................................... 17l IV. The Supra-renal Capsules............................ j-j The Kidneys........................... j-. The Diaphragm.................................... j-7 CONTENTS. IX DISSECTION PAGE IV. Anatomy of Femoral Hernia................................ 178 The Lumbar Plexus....................................... 182 V. Anatomy of the Perineum.................................. 184 VI. Interior of the Pelvis....................................... 188 VII. The Rectum................................... .......... 194 The Bladder.............................................. 195 Vesiculse Seminales and Prostate Gland..................... 196 The Penis................................................ 197 The Testes................................................ 199 Female Organs of Generation............................... 201 Vni. Anterior Femoral Region................................... 205 IX. Gluteal Region............................................ 211 X. Posterior Femoral Region...................................215 Popliteal Space............................................ 216 XL Front of the Leg and Dorsum of the Foot.................... 218 XII. Back of the Leg........................................... 221 XIII. Sole of the Foot........................................... 225 XIV. Ligaments of the Pelvis and Lower Extremity................ 229 Peculiarities in the Anatomy of the Foetus........................236 A FEW GENERAL RULES TO BE OBSERVED IN DISSECTING. The necessary incisions to expose any part, whilst they follow as nearly as may be the direction of, and penetrate through to, the muscular fibres underlying them, should be so arranged as to preserve the skin in the largest possible flaps, as no covering of the dissection, when temporarily abandoned, preserves it in so good a condition. The skin is to be removed only so far as free- dom of dissection, in any given region, requires. The fingers should take the place of the forceps as soon as the skin is suffi- ciently raised, as they stretch it more evenly and over a greater extent of surface than the former. In dissecting muscles, the fibres must always, if possible, be made tense. The sheath of a muscle should as a rule be detached with the skin and never left behind for subsequent removal. The knife should operate in long sweeps, with the whole of its convexity and not by its point, following the direction of the fibres, the dissection of any one bundle of which should be com- pleted in its whole length before a second is commenced. The forceps must never seize the muscular fibres, as by so doing they become torn and present a ragged appearance. The deep surface of a muscle is to be cleaned as thoroughly as its superficial; the tendinous extremities are to be isolated with special pains that their points of attachment may be precisely studied. When muscles are to be divided, the section should always, if practi- cable, be made in the central portion and never at one of their xii GENERAL RULES. attachments ; the two ends may then at any time be reapplied? and the deep relations, especially to articulations, can thus be better appreciated. Arteries should be dissected with a pointed knife and so far as is practicable from the trunk towards the branches, and the branches from their origin towards their termination. The for- ceps should steady the artery by seizing its sheath, and not the vessel itself; if the forceps are what they should be, this rule need never be violated; inferior forceps area greater hinderance to neat dissecting than dull scalpels. Nerves are to be put upon the stretch with hooks, and stripped of their cellular sheath with care, as its color so identifies it with the nerve itself, that the latter is liable to be unintentionally divided. The subject, when not in use, should be covered entirely, (with a sheet of india-rubber cloth, if it is to be had ;) and each part, with the integument belonging to it, replaced, by a bandage dampened, not wet, with water. Parts intended to be preserved for the study of the ligaments must be kept merely moist enough to prevent drying; any thing like maceration giving all the tis- sues a uniform opacity which renders the distinction of the liga- ments at once difficult and unsatisfactory. Slowness, without unnecessary delay, and industrious, syste- matic application, completing whatever is commenced, before be- ginning elsewhere, are requisites for good dissecting. Neatness and cleanliness, both as to the table and the part dissectin», as well as the hands of the dissector, will contribute, not only to personal comfort, but to the avoidance of diarrhoea and dissecting wounds. Collodion makes a good coating for any accidental abrasions which may exist before commencing to dissect. If a wound is re- ceived whilst dissecting, it should immediately be held beneath the running water-faucet and thoroughly washed; the bleedino must be encouraged and any matter introduced drawn out by GENERAL RULES. xiii sucking the part. It is a questionable practice to cauterize such wounds, but if it be done, a saturated solution is the only form in which nitrate of silver should be used. The following recapitulation may be said to comprise the Maxims for the Dissecting Room. I. Cover the part with damp cloths after dissecting. Drying is worse than decomposing. II. Put all fragments on a piece of paper, which, with all fluids, are to be removed as they accumulate. ni. Make every thing tense, if possible, before dissec- tion, AND COMPLETE THE DISSECTION OF ONE THING THOR- OUGHLY, BEFORE ANOTHER IS COMMENCED. IV. Never leave a muscle till you come to bone at both ends,—if there is bone. V. LET THE EYE GO BEFORE THE HAND, AND THE MIND GO BEFORE THE EYE. VI. Know what the books say, and cross-examine them in presence of the subject. PART FIRST. ANATOMY OF THE HEAD AND NECK. Thp dissection of the regions included under the general term of " the head " is considered the most difficult of any in the body; comprising more important struc- tures within smaller limits than any other part, and the skeleton, constituting so large a portion of their bulk, it presents mechanical obstacles not easily surmounted. It is hardly possible to get an idea of all the different component parts in one dis- section, as may be done in other regions of the body; the muscles and arteries may be got out upon one side of the head, and the other half reserved for the nerves; a special part is. however, desirable for the dissection of the nerves; it should not be injected, and it is well to preserve it in spirit, so slowly is their preparation accomplished. DISSECTION I. EXTERNAL EAR. The dissection is usually commenced by an examination of the muscles of the ear; for this purpose the head rests upon its side, and the hair should be shaven from the scalp. A hook inserted into and drawing down the upper margin of the ear, brings into relief two bands extending to the side of the head; the skin over these, with the cellular tissue beneath it, being cautiously removed, the delicate muscular fibres, of which they are composed, will be revealed. This dissection is sometimes made puzzling to the beginner by the pale color and small size of the aural muscles. The muscles that attach the car to the side of the head are called the extrinsic muscles ; the special muscles of the cartilage are called intrinsic. The Attrahens Aurem is the most anterior of the extrin- sic muscles; it arises, fan-shaped, from the epicranial aponeuro- sis, and its fibres are directed backwards to be inserted into the 1 2 ANATOMY OF THE HEAD AND NECK. anterior part of the rim of the ear. It is often wanting, or its place is supplied by the anterior fibres of the attollens au- rem. The Attollens Aurem is better marked than the preced- ing; it arises from the epicranial aponeurosis, and is inserted into the upper part of the concha of the ear. The ear is now lo be drawn forwards by the hook, when another band in relief will mark the position of the posterior muscle. The Retrahens Aurem arises by several separate slips from the mastoid process of the temporal bone, and is inserted into the posterior surface of the concha. In dissecting these muscles the anterior auricular artery, a branch of the temporal, and the posterior auricular, a branch of the occipital, will be seen; they are distributed as their names in- dicate. The following nerves should be sought for in this connection : The posterior auricular, a branch of the facial nerve, accompanies the artery of the same name and anastomoses with the auricularis magnus nerve, one of the ascending branches of the anterior cervical plexus ; it is distributed to the ear and occipital region. The occipitalis major nerve, a posterior branch of the second cer- vical nerve, emerging from the deep muscles of the back of the neck, and accompanying in part of its course the occipital artery, sends a branch to the ear. The occipitalis minor, another ascend- ing branch of the anterior cervical plexus, is placed midway be- tween the last named and the posterior auricular, with both of which it communicates; it supplies the attollens aurem and the integument. The external ear is described as consisting of the pinna and the meatus. The pinna consists of a number of folds and hol- lows, which have been named as follows: the external folded margin is called the helix; the elevation that runs parallel to it, the anti-helix; the process projecting over the meatus is the tragus; opposite to this is a prominence called the anti-tragus; the dependent portion of the ear is called the lobule ; the central depression around the meatus is the concha; the space between the helix and the anti-helix, the fossa innominata; this termi- nates anteriorly in a triangular depression called the scaphoid fossa. FRONTAL AND ORBITAL REGION. 3 The muscles of the pinna require a patient dissection in a strong light; indeed they are not always to be found, being only rudimentary in man. The integument covering them is very thiu and delicate. The major helicis is to be found on the anterior border of the helix, just above the tragus. The minor helicis is placed upon that part of the rim of the ear which extends into the concha. The tragicus is a bundle of transverse fibres situated on the tragus. The anti-tragicus arises from the outer part of the anti-tragus, and is inserted into the pointed extremity of the anti-helix. The transversus auriculm is found on the posterior aspect of the ear, stretching transversely across the depression between the helix and the concha. On removing all the integument, the pinna of the ear will be found to consist of a single cartilage, presenting the general out- lines of the ear in its natural state, but considerably diminished in size. It is firmly attached to the processus auditorius of the temporal bone by a cartilaginous tube called the meatus; the upper and lower halves of which are imperfect, being completed by fibrous tissue. In the subcutaneous cellular tissue of the meatus are the ceruminous glands, which secrete the wax of the ear. To obtain a perfect idea of the external auditor canal, a plaster or wax cast of it should be made; the canal being previously cleared of all accumulated cerumen, and oiled with a feather, the cast when hardened will be easily extracted. FRONTAL AND ORBITAL REGION. To dissect the occipito-frontalis muscle, make an incision from the root of the nose backwards to the occiput; this should be met by an incision made from the ear at right angles to it; another passes along the eyebrow from the root of the nose outwards. The flap is lifted from the nasal angle, and with great care; for the fibres are with difficulty traced, and the thin plane which they constitute is liable to be cut through and dissected up from the bone upon which it lies; the aponeurotic tendon which expands over ihe vertex of the skull can hardly fail of being disfigured with " button holes." The Occipito-frontalis Muscle consists of two portions, a frontal and an occipital; the two being connected by an aponeu- rosis, which expands over the vertex of the cranium. It may therefore be described as arising from the superior curved line of the occipital bone, and from the mastoid process of the temporal 4 ANATOMY OF THE HEAD AND NECK. bone to form a rounded and flat belly, which terminating in an aponeurosis, passes forwards to join the frontal portion lying upon the frontal bone, which, broader and thinner than the occip.ta , confounds itself with the orbicularis palpebrarum, PJ18^" nasi and corrugator supercilii, and is inserted into the nasal bones and the superciliary ridge of the frontal bone. It mi-ht seem better, perhaps, to describe this as two muscles instead of one single digastric muscle; each being inserted into the epicranial aponeurosis. This would be suggested by its ac- tion, it being a muscle of expression, and is the manner in which it is described by some authors. The Pyramidalis Nasi is a slip of the occipito-frontalis passing downwards upon the bridge of the nose. Its outline is usually confused, and it is inserted into the nasal bone and the compressor muscle of the nose. Properly, it should be con- sidered as a pillar of origin of the frontal belly of the occipito- frontalis. The Orbicularis Palpebrarum surrounds the eye, and is seen by dissecting the integument from the eyelids, upon which it expands, as it also does upon the orbit; it is a thin muscular plane, difficult to dissect, owing to the want of fixedness in the parts'upon which it rests. Its fibres are well marked, and it arises from the inner angle of the frontal bone, the nasal pro- cess of the superior maxillary and the tendon of the tarsal cartilages attached to the latter point; encircling the orbit, it is inserted into the same point from which it arose, thus making a sphincter muscle. The Corrugator Supercilii lies beneath the upper half of the orbicularis palpebrarum, which must be dissected up in order to expose it. It is usually confounded with the orbicularis, and not always to be satisfactorily separated from it. It arises from the inner part of the superciliary ridge, and is inserted into the under surface of the orbicularis and frontal muscle, being about an inch in length. Upon the frontal bone, beneath the muscles last dissected, will be found the divisions of the supra- orbital nerve, a branch of the fifth cranial pair; it emerges from the supra-orbital notch, and after supplying the muscles which lie over it, is distributed to the epicranium and integument of the forehead. This nerve is accompanied by the supra-orbital branch FRONTAL AND ORBITAL REGION. 5 of the ophthalmic artery, itself a branch of the internal carotid; emerging at the supra-orbital foramen, it is distributed like the nerve. Upon the posterior belly of the occipito-frontalis musele will be found the occipitalis major nerve, a posterior branch of the second cervical nerve, and the occipital artery from the exter- nal carotid. The artery is tortuous, and supplies the muscle, integument, and epicranium; it anastomoses with the temporal artery and gives off the posterior auricular branch to the exter- nal ear. The nerve accompanies it only in a part of its course, and is distributed chiefly to the integument. The Eyelids consist of two cartilages, one for the upper and one for the lower lid, covered externally by muscles and integu- ment ; the cartilage of the upper lid is the largest; both are semi- lunar in shape, and attached to the edge of the orbit by a mem- brane called ligamentum palpebral. A small fibrous band, called the tendo oculi, arising from the anterior margin of the lachrymal canal and dividing into processes, one for each cartilage, fixes them internally ; a fibrous band also attaches them to the margin of the orbit externally. They are invested internally by a mucous membrane called the conjunctiva; this is continuous with that of the eyeball from which it is reflected; and on both surfaces is movable and vascular; over the cornea it is thin and transparent, and in the state of health no vessels are traceable in that part. On the ocular surface of the cartilages may be seen numerous parallel and somewhat tortuous lines, indicating the Meibomian glands, which open along the free edge of the eyelids. The lachry- mal canal has an opening at the inner extremity of each eyelid, indicated by a slight prominence, in the centre of which is the small orifice called punclum lacrymale. In the internal commis- sure of the eyelids there is a prominent reddish body formed from the conjunctiva, and called the caruncula lacrymalis; just ex- ternal to this is a fold of the conjunctiva, called plica semilunaris, in which may sometimes be found a minute cartilage ; this is con- sidered as corresponding to the third lid or membrana nictitans of birds. The eyelids are supplied by the palpebral arteries, branches of the ophthalmic, given off near the inner angle of the orbit; the nasal, another branch from the same source, emerges above the tendo oculi, and inosculates with the angular branch of the facial 6 ANATOMY OF THE HEAD AND NECK. artery; the frontal, also from the ophthalmic, appears near the same point, and goes to the forehead. The Lachrymal Gland is situated in the hollow of the exter- nal angular process of the frontal bone, and admits of exami- nation at this time by dividing the upper eyelid at its centre and externally. It is a thin flattened gland, resembling in its struc- ture the salivary glands; it sends a prolongation down upon the cartilage of the upper eyelid, but its principal portion lies in contact with the periosteum, to which it is held by a few fibrous bands; its inferior surface rests upon the eyeball, and the external rectus muscle. Its excretory ducts cannot be demon- strated. To see Horner's muscle, the eyelids must be divided in the middle by a transverse cut and turned towards the nose; the conjunctiva with the fat and cellular tissue filling the inner angle of the eye must be dissected away. The Tensor Tarsi or Horner's Muscle consists of a quadri- lateral plane of delicate fibres, closely applied to and arising from the lachrymal bone; it is about four lines wide and six lines long; anteriorly it splits into two bands, which terminate in very delicate tendons to be inserted into each tarsal cartilage along its lachrymal duct. DISSECTION n. FACIAL REGION. In order to dissect the muscles of the face, the lips and cheeks should be dis- tended by filling the space between them and the teeth with cotton wool or like material; the lips are then to be sewed together; the nostrils may be distended in the same manner. One side should be dissected at a time, the oiher half being pres-rved to verify the first: this is a considerable advantage, for the very feeble develop- ment of the facial muscles makes them difficult to distinguish; the class of individ- uals who finish their career iu the dissecting-room, are not the ones calculated to show the muscles of expression about the nose and mouth, as they do those of the arms or legs. The integument should be turned downwards from the inner side of the orbit; and as the inferior segment of the orbicularis palpebrarum muscle covers in the origin of several facial muscles, it should be dissected up so as to expose th-m. The Levator Labii superioris, ala:que Nasi occupies the depression at the side of the nose ; it arises from the nasal process FACIAL REGION. 7 of the superior maxillary bone, and expanding as it descends, is attached to the ala of the nose and the surface of the upper lip. The fibres attached to the ala of the nose are often but a small part of the whole number, and few and faint in appear- ance. The Levator Labii superioris proprius is a quadrilateral muscle, covered in by a considerable amount of adipose tissue, and partially obscured by the preceding muscle and the orbicu- laris palpebrarum; it is a very distinctly characterized muscle, arising from the edge of the orbit and the surface of bone be- neath, and is inserted into the integument of the upper lip by fibres which become confounded with the orbicularis oris. Beneath this muscle will be found the branches of the infra- orbital nerve; being the terminal filaments of the superior max- illary branch of the third pair of cranial nerves; it emerges at the infra-orbital foramen, and expanding on the side of the nose and upper lip, freely anastomoses with the branches of the facial nerve. This nerve is accompanied by the infra-orbital vein, and by one of the terminal branches of the internal maxillary artery, called the infra-orbital; this emerges also at the infra-orbital for- amen, and is distributed like its accompanying nerve, anastomos- ing with the facial artery. The Zygomaticus minor Muscle is the internal one of two slender muscular slips passing from the malar bone to the angle of the lips; it arises from the face of the malar bone and passes obliquely to the integument of the lip, near its angle, where it is inserted. This muscle is very often wanting,—and, when present, seems to be a bundle of fibres of the orbicularis palpebrte detached, to pass downwards to the angle of the lips. The Zygomaticus major Muscle arises outside the preced- ing, from the surface of the malar bone near its external angle, and is inserted into the integument of the angle of the lips. As its name implies, this is considerably larger than its companion. The Levator anguli Okis arises from the canine fossa of the superior maxillary bone, and is covered in by the levator labii superioris proprius ; it is inserted into the angle of the mouth, where it confounds itself with the orbicularis oris and the other muscles converging at that point. The Depressor Labii superioris al.equk Nasi can only 8 ANATOMY OF THE HEAD AND NECK. be seen by turning the upper lip inside out and dissecting off the mucous membrane on each side of the frenum ; it is a small pale muscle, not easily detected, the fibres of which are con- founded with those of the orbicularis oris ; it arises from the fossa in the superior maxillary bone just above the incisor teeth, and is inserted into the upper lip and the cartilages of the ala and sep- tum of the nose. The Compressor Nasi expands in a radiated manner upon the side of the nose; its fibres are very thin and pale, and its origin is covered in by the levator labii; it arises from the canine fossa of the superior maxillary bone, and ends in an aponeuro- sis covering the cartilaginous part of the nose, joining the tendon of the other side: its precise limits are difficult to establish. The Cartilages of the Nose are five in number, two being on the sides and one in the centre, forming the septum of the nos- trils. The superior ones are called the lateral fibro-cartilages; they are triangular in shape, and are attached to the nasal bones and the nasal process of the superior maxillary bone ; they unite upon the median line. Below these are the alar fibro-cartilages ; these are curved in such a way as to form the rim of the nostril; anteriorly with its fellow, it forms the apex of the nose, and its inner portion at this part projects backwards along the septum nasi. This cartilage has no osseous attachment, but is connected by fibrous tissue with the lateral cartilages and the intendment. To the outer curve of the alar cartilage are attached several small cartilages connected with each other by fibrous tissue ; these are called the sesamoid cartilages. The septum nasi is triangular in form and divides the nose into its two nostrils: it is attached above to the nasal bones and lateral cartilages, posteriorly it unites with the vomer, and below with the palate process of the superior maxillary bones. The Orbicularis Oris is an elliptical-shaped muscle forming a sphincter round the mouth; it has no osseous attachment: the fibres of the two halves cross each other at the angles of the mouth; those belonging to the upper lip join the lower portion of the buccinator muscle, and those from the lower lip join with the upper part of the same muscle. Beneath this muscle lies the mucous membrane of the lips, and between this and the muscular fibres are the coronary branch of the facial ar- FACIAL REGION. 9 tery, and numerous small, rounded mucous glands, called labial glands. The Depressor Labii inferioris, or Quadratus Menti, arises from the oblique line of the inferior maxillary bone, and is inserted into the orbicularis oris at the central part of the portion belonging to the lower lip. The Depressor anguli Oris, or Triangularis Menti, arises more externally from the same oblique line of the inferior maxillary bone, and is inserted into the orbicularis near the angle of the lips; its most external fibres may be traced as continuous with some of those of the zygomaticus major. Both of the last-described muscles are made up of fibres from the platysma myoides of the neck ; and if they have been care- fully dissected, the continuity may be traced with the greatest ease. Beneath the depressor anguli oris will be found issuing from the mental foramen, the termination of the inferior dental branch of the superior maxillary trunk of the third pair of cranial nerves; its filaments supply the muscles and integument of the lower lip and anastomose with the facial nerve. The inferior dental branch of the internal maxillary artery and its accompanying vein also emerges at the mental foramen, and, communicating with the facial artery, is distributed to the structures covering the lower jaw. The Levator Labii inferioris is an extremely small muscle, difficult to isolate; it is to be sought from the inside of the under lip, which should be turned down and the frenum divided. The muscle arises from the surface of bone just below the incisor teeth, and is inserted into the integument on the tip of the chin. The Buccinator Muscle arises from the outer surface of the alveolar borders of the upper and lower jaw, as far forwards as the first molar tooth, also from a fibrous raphe called the pterygo- maxillary ligament, which intervenes between it and the superior constrictor of the pharynx; its fibres converge anteriorly and become continuous with those of the orbicularis oris. The inter- section of these muscles anteriorly should be dissected with spe- cial care. At about its centre, the buccinator is perforated by the excretory duct of the parotid gland; this lies partly imbedded in a considerable quantity of fat which occupies the interval be- 10 ANATOMY OF THE HEAD AND NECK. tween this muscle and the masseter, and care must therefore be taken not to divide it. The Risorius Santorini Muscle consists of a few fibres of the platysma myoides, varying in their degree of distinctness, which pass transversely inwards over part of the buccinator and masseter muscle, to terminate near the angle of the mouth. FACIAL ARTERIES. The facial arteries may be made the subject of a special dissection upon the other side of the face; or if the student has been careful to preserve them in connection with the muscles, they may be studied on the side already dissected. The arteries proper of the face, are the facial and transverse facial; the former a branch of the external carotid, the latter of the temporal artery. The Facial Artery emerges from the neck just anterior to the masseter muscle, where it rests upon the lower jaw, covered in by the platysma myoides; it passes upwards obliquely and tor- tuously : near the angle of the mouth it gives off' an inferior labial branch, which passes beneath the depressor anguli oris muscle, and is distributed to the lower lip and chin. The superior and infe- rior coronary branches are given off separately, or by a common trunk; they supply the upper and lower lip, lying between the orbicularis oris muscle and the mucous membrane, and inosculate with the corresponding branches of the other side. The superior coronary sends a branch to the septum of the nose. The facial continues up beside the nose under the name of the lateralis nasi, its termination being called the angular artery, and anastomoses with the nasal branch of the ophthalmic. The facial artery is apt to be irregular, and is seldom symmetrical on the two sides of the face. The facial vein accompanies the facial artery on its outer side, and ends in the internal jugular vein. The Transverse Facial Artery is a branch of the temporal artery; it emerges at the anterior border of the parotid eland, and lies beside the parotid duct; it anastomoses with the facial artery, and supplies the muscles and integument. It occasionally arises from the external carotid. facial nerves. If a special part is not to be obtained for the dissecti >» of the facial nerves, they may be examined on a side of the face reserved for that purpose, or, if sufficiently PAROTID GLAND. AND REGION. 11 preserved, in connection with the dissections already made. Some of the nerves are concealed by the parotid gland, but a greater part are external to it; the exter- nal branches are to be followed out one by one, and, to see those within the gland, it must be removed piece by piece whilst tracing them backwards. The Facial Nerve is a portion of the seventh cranial nerve, and issues from the skull at the stylo-mastoid foramen; it divides near the ramus of the jaw into two divisions, the temporo-facial and the cervico-facial; the posterior auricular branch, which was dissected with the external ear, is given off close to the skull, and turns upwards in front of the mastoid process to supply the attra- hens and attollens aurem and the posterior belly of the occipital muscle. The temporo-facial division gives off a large number of filaments which expand upon the side of the face as temporal, malar, and infra-orbital branches, anastomosing freely with the supra-orbital and infra-orbital branches of the fifth cranial nerve. The cervico-facial division is smaller than the preceding; its filaments are distributed upon the lower part of the face as buc- cal, supra-maxillary and infra-maxillary branches; the supra- maxillary branches course inwards towards the chin and be- neath the depressor anguli oris anastomose with the inferior dental branch of the fifth nerve. The web-like aspect of this network of communicating branches, has given them collectively the name of pes anserinus. The auriculo-temporal branch of the inferior maxillary trunk of the fifth pair is also partly seen in this dissection; it emerges from beneath the parotid gland and ascends in company with the temporal artery to the top of the head; it communicates with the facial nerve and supplies the integument in front of the ear, the terminal branches being distributed to the epicranial and tempo- ral aponeuroses. parotid gland and region. The Parotid Gland, the largest of the salivary glands, is an irregularly shaped body made up of lobes and lobules ; it is lim- ited above by the zygomatic arch, behind by the meatus of the ear and the sterno-mastoid muscle; inferiorly, it descends as low as the digastricus muscle, and its deep surface penetrates in various directions to a considerable depth; anteriorly, it expands into 12 ANATOMY OF THE HEAD AND NECK. the face and has a small accessory part prolonged from it over the masseter muscle. Its excretory duct, called the duct of Steno, is given off from its anterior portion ; it can be traced but a short distance into the substance of the gland itself; the length of the duct is about two inches and a half, and its size is about equal to that of a crow quill. It isvcomposed of a fibrous and a mucous coat, and perforates the cheek obliquely opposite the second molar tooth of the upper jaw. A line drawn from the meatus audito- rius to a little below the nostril would mark the level of the duct in the face, and its orifice would correspond to a spot midway between these two limits. The internal carotid artery and inter- nal jugular vein lie beneath the gland ; the external carotid, ac- companied by several large veins, passes through its middle, send- ing off numerous branches ; curving from behind forwards is the facial nerve. Its own vessels and nerves are derived from the external carotid and the facial nerve. The examination of the parotid will demonstrate the impossibility of completely extirpating this body during life; even in the dead subject it will be found that it is a very nice dissection to remove it neatly and properly. The scissors will be found useful instruments in this operation, which should be commenced from the external carotid; the branches of this, many of which are small, should all be saved, so that when the gland is removed the artery shall be left with all its offsets smooth and unbroken. The Masseter Muscle arises from both surfaces of the zy- goma and from the malar bone, and is inserted into the angle and outer surface of the coronoid process of the inferior maxillary bone. In shape this muscle is quadrilateral; externally it is covered by a strong shining aponeurosis obscuring its muscular fibres, and which is not to be removed. The direction of the su- perficial fibres of this muscle is obliquely backwards; of its deeper fibres obliquely forwards. The Temporal Aponeurosis is a brilliant fibrous membrane covering in the temporal muscle: it is attached superiorly to the curved line that limits the temporal fossa, and below it is fixed to the zygoma: it is continuous with the epicranial apo- neurosis. The Temporal Artery ramifies upon the temporal aponeuro- sis ; it is one of the terminal branches of the external carotid, arising within the parotid gland, where it sends off the trans- verse facial branch (p. 10). Ascending upon the temporal fas- DURA MATER AND SINUSES. 13 cia, just above the zygoma, it sends a small branch, called the middle temporal, through the fascia to the muscle, and then divides into two branches, anterior and posterior; the anterior is distributed in a very tortuous manner to the forehead, where it anastomoses with the supra-orbital branch of the ophthalmic artery ; the posterior passes backwards to the occiput, where it anastomoses with the occipital artery. The temporal aponeurosis is to be incised around its edges and removed; the zy- goma is to be cut through with a chisel just in front of the ear and at its union with the malar bone in front of the masseter muscle; this muscle being partially detached from the surface of the ramus of the jaw, and turned downwards with the portion of the zygoma, and a layer of fat and soft cellular tissue removed, the whole temporal muscle will be exposed. The Temporal Muscle arises from the temporal aponeurosis and from the surface of the depression on the side of the skull known as the temporal fossa. Its fibres converge to a superficial tendon, which is inserted into all the inner surface of thecoronoid process of the inferior maxillary bone, from fts apex to near the last molar tooth. DISSECTION III. dura mater and sinuses. We now proceed to the removal of the calvaria, which may be accomplished by breaking through the skull on a line just above the frontal sinuses and the tops of the ears, with the sharp part of a French hammer, or it may be done more neatly with a saw guided in the proper direction by a string tied round the head. The saw is to be carried through the outer table of the bone only, and the inner one fractured by a chisel and mallet; this saves the membranes of the brain from being wouuded, but does not leave the bones in so neat a condition for preservation, when that is intended. The sensation communicated to the hand by the saw, and the color of the bone-dust, tells the operator when he has got through the outer and reached the vascular diploe between the two tables. A hook or chisel is to be in- troduced into the line of the incision when it has been completed. The applica- tion of very considerable force will be required, by either prying or pulling, for the detachment of the calvaria from the membranes adherent to it. The Dura Mater is the most external of the cerebral mem- branes ; it acts as periosteum to the bones and a support to the brain ; it is rough externally, where it is torn from the calvaria, 14 ANATOMY OF THE HEAD AND NECK. and especially so along the line of the sutures; parts of it are sometimes left adhering to the detached calvaria. Along the median line some small fibrous bodies, called Pacchionian glands, will be noticed; they are wanting in infancy and most numerous in old age; depressions in the bone corresponding to them will sometimes be found; these depressions were described by some old authors as resulting from caries. The dura mater should be divided with scissors along the mar- gin of the skull except on the median line in front and behind. The two flaps thus formed may be turned up on to the top of the brain. It will now be seen that its inner surface is smooth and polished; this is due to a serous coat which is the parietal part of the arachnoid, a serous membrane investing the brain and re- flected upon the dura mater, and which will be more particularly spoken of hereafter. The dura mater is therefore a, fibro-serous membrane. By separating the hemispheres of the brain it will be seen that a process of the dura mater penetrates between them: this is called the falx cerebri. Narrow in front, this is attached to the crista galli of the ethmoid bone; broader pos- teriorly, it is attached to a horizontal expansion of the dura mater called the tentorium; its superior border is attached alone the vertex of the skull, and the inferior, which is concave and free, is in contact with the corpus callosum of the brain. The falx sometimes presents perforations of various sizes, or a rarefaction of its fibres, which gives it a lace-like appearance; more rarely a solution of continuity, sufficient to allow the hemispheres of the brain to come in contact with each other, has been noticed. The superior longitudinal sinus occupies the convex border of the falx, and may be laid open with the scissors; it extends from the crista galli to the occipital protuberance, is triangular in shape, and perforated by numerous small veins ; in its interior transverse fibrous bands, called chorda Willisii, cross it here and there, and occasionally Pacchionian glands are found within the sinus. It terminates posteriorly, in common with other sinuses, at a point called the torcular Iferophili. The in- ferior longitudinal sinus occupies the concave border of the falx; this terminates in the straight sinus of the tentorium, which also continues to the torcular Herophili. The straight DURA MATER AND SINUSES. 15 sinus receives the venoe, Galeni, which come from the interior of the brain. The brain must now be removed. The head should be allowed to depend as much as possible, and the operation is to be commenced by the division of the anterior attachment of the falx; this is to be raised and thrown backwards, but not detached posteriorly; in reflecting this, several veins, entering the superior longitudinal sinus, will necessarily be divided. The examination of the arteries at the base of the brain is not always easy in the subject which is used lor the other parts to be studied in the same region; as, unless care is taken to leave them behind in removing the brain, a portion of them will remain attached to it. If the brain is too soft to be examined with benefit, it is much better to leave the arteries in connection with the skull. The softened cerebral matter left attached to them may be best removed by a stream of water from a syringe or squeezed sponge. In a fresh brain, or one that will harden well, they should be studied in connection with the base of the brain; in that connection they will be described. The anterior lobes are to be carefully lifted by the fingers, together with the olfac- tory bulbs'from each side of the crista galli. The carotid arteries, optic and motor oculi nerves are to be divided on each side of the processus olivaris, and the pituitary gland lifted out of the sella turcica; this sometimes cannot be done, and then its ped- icle must be divided. The hemispheres being supported in the left hand, and grad- ually allowed to roll out of the cranial cavity, the tentorium is brought into view, and just in front of its anterior margin, the fourth or patheticus nerve; this is divided, and also the tentorium, close to its attachment to the temporal boue. The fifth nerve is next brought into view; the sixth, small and slight, near the median line of the clivus Blumenbachii; more externally the seventh pair, composed of two parts, the facial and auditory; below this the three trunks of the eighth pair; the upper being the glosso-pharyngeal, the flat band next below the pneumogastric; and the one ascending from the spinal canal the spinal accessory. These being all divided, as well as the ninth, which is the remaining one, the vertebral arteries are to be cut off close to the spinal cord. The spinal cord is then separated with the spinal nerves on each side as far down the canal as possible, and the brain will then roll out of the cranial cavity. The brain should be laid in a basin with the base uppermost; it should be im- mersed in alcohol to harden and preserve it, and covered with a piece of doubled cotton cloth. The cloth will keep it wet by imbibition, if there is not alcohol enough to cover it. It is, however, to be borne in mind that the brain softens very soon after death, and that, unless early removed, it may be unfit for dissection. A portion of each hem- isphere may be shaved off, in order to give the spirit a better chance to penetrate; but even this may not prevent its decomposition in some of its deep-seated parts. The autopsy-room is the best place for the study of the brain, as it cau always there be seen in its fresh and naturally firm condition. The dura mater at the base of the cranial cavity will be found very adherent, on account of the sutures into which it penetrates, and the foramina through which it is continued to form the sheath of the nerves; it is also prolonged downwards into the spinal 16 ANATOMY OF THE nEAD AND NECK. canal. The tentorium, if replaced, will be found to separate the spaces occupied by the cerebrum and cerebellum, and to be attached along the transverse groove of the occipital bone, the petrous portion of the temporal bone, and the posterior clinoid processes of the sphenoid. In the attachment of the tentorium to the occipital bone, will be seen the lateral sinuses; at the base of the petrous portion of the temporal bone, these sinuses turn downwards and pass through the posterior foramen lacerum ; just before entering the foramen the inferior petrosal sinus joins the lateral sinus, and the two united become the internal jugular vein. The inferior petrosal sinus is the continuation backwards of the cavernous sinus; it passes along the lower border of the petrous portion of the temporal bone, and terminates as above described. The superior petrosal sinus is of small size, and lies along the upper border of the petrous bone in the attached portion of the tentorium; it establishes another communication between the cavernous and lateral sinuses, by entering the latter near the base of the petrous bone. Projecting below the tentorium is the falx cer.ebelli, which sep- arates the two hemispheres of the cerebellum as the falx cerebri does those of the cerebrum; it ends at the foramen magnum, and is attached along the middle line of the occipital bone. In the attached border of this falx may be found two small sinuses, called the occipital sinuses, which terminate in the torcular Hero- phili. The cavernous sinuses are situated on each side of the sella turcica, and are so called from the existence, in their interior, of trabecula;, like those of cavernous structures in other parts of the body. In the internal wall of the sinus is the internal carotid artery, covered by minute nervous filaments of the carotid plexus of the sympathetic nerve, and crossed by the sixth or abducens nerve; in the external wall of the sinus are the third, (motor oculi,) fourth, (trochlearis,) and ophthalmic branch of the fifth or tri- facial nerve. The cavernous sinuses of the two sides are connected by the circular sinuses, which surround the pituitary gland; the trans- verse, or basilar sinus, which lies upon the basilar portion of the occipital bone, sometimes unites the cavernous and sometimes DURA MATER AND SINUSES. 17 the petrosal sinuses; anteriorly, they receive the ophthalmic veins. The Pituitary Body should be sought for in the sella tur- cica and removed for examination. It is a reddish gray, solid body, closely fixed in its location by the dura mater ; it is com- posed of two lobes, the anterior of which is the largest; and is con- nected with the infundibulum of the brain by a peduncle, which should be noticed. In the foetus the pituitary body is hollow, and communicates with the third ventricle through the infundibulum. It was by virtue of this communication that Vesalius believed the fluid of the ventricles was transmitted to the pituitary body, and from it through the sphenoidal sinuses to the nasal fossae, thus causing the disease called pituila, or catarrh ; a theory that char- latans still find for their advantage to maintain. The dura mater is supplied by a number of arteries called ■ meningeal. The anterior meningeal, an offset from the ethmoid branch of the internal carotid, is a small artery which enters the skull by a foramen between the ethmoid and frontal bones, and is distributed to the dura mater in that vicinity. The middle menin- geal artery is a branch of the internal maxillary; it enters the skull by the spinous foramen of the sphenoid bone, and passing into a deep groove in the inferior angle of the parietal bone. spreads over the side of the cranial cavity ; the meningea parva, from the same source, enters by the foramen ovale, and is distrib- uted to the middle cranial fossa. The inferior meningeal arteries are branches from the ascending pharyngeal and occipital, which enter by the foramen lacerum, and, together with the posterior meningeal, from the vertebral artery, supply the posterior cranial fossa. The vertebral arteries will be seen entering the foramen mag- num, piercing the dura mater. The arteries of the two sides converge around the medulla oblongata, and become united in one trunk, the basilar, which will be described with the base of the brain. The vertebral artery gives off many small branches, and one of some size, the posterior meningeal, to the cerebellar fossa and the falx cerebelli. . The internal carotid artery appears in the base of the skull, at the apex of the petrous portion of the temporal bone ; given off from the common carotid in the neck, it ascends to the carotid 2 18 ANATOMY OF THE HEAD AND NECK. foramen in the temporal bone, and pursuing a tortuous course in an osseous canal through that bone, enters the cranial cji v The cranial part of the vessel describes an S-like curve at the side of the sella turcica where it lies in to™*™™™™'"™ the anterior clinoid process it gives off the ophthalmic artery and then, turning upwards, divides into branches to supply he brain. As it winds through the cavernous sinus it W surrounded by nervous plexuses derived from the sympathetic nerve of the neck ; the branches of these plexuses are very minute, and man injected subject would not be likely to be found ; they are called the carotid and cavernous plexuses, the former being on the outer side at the entrance of the sinus, and the latter close to the root of the anterior clinoid process, which should be cut away to ex- amine it. arteries and muscles of the orbit. In order to get at the ophthalmic artery and other contents of the orbit, the frontal bone shou.d be cut down on each side, and the two incisions continued backward with a chisel till they meet near the optic foramen; the bone being removed the orbit is exposed, filled with a soft delicate fat. The muscles and arteries require patience for their dissection; these may be dissected upon one s.de and the nerves upon the other. The eye of any large animal, if removed with all the conten s of the orbit, permits the verification, on a larger scale, of many of the points about to be described. The ophthalmic artery enters the orbit at the optic foramen on the outer side of the optic nerve; it gives off numerous small branches not always, however, injected. Its first branch is the lach- rymal ; this lies along the upper border of the external rectus mus- cle, in company with the lachrymal nerve ; it is distributed to the lachrymal gland and eyelids. The supra-orbital branch rests upon the levator palpebrae muscle, and passes through the supra-orbi- tal foramen, where it expands upon the forehead, and is distrib- uted to the muscles and integument. The ethmoidal branches, two in number, pass through the ethmoidal foramina, and are dis- tributed to the dura mater and nasal fossa?. The palpebral are oiven off from the main trunk near the eyelids, to which they are distributed. ^ The frontal branch emerges at the inner angle of the eye, and is distributed to the forehead. The nasal also emerges at the inner angle, and divides into two branches, one of which anastomoses with the angular or terminal branch of the ARTERIES AND MUSCLES OF THE ORBIT. 19 facial, and the other under the name of dorsalis nasi is distrib- uted to the nose. The muscular branches supply the muscles, and give off some small twigs to the eyeball, called anterior cili- ary. The short ciliary branches enter the eyeball around the optic nerve; two of these, one on each side, piercing the scle- rotic, farther forwards, are called the long ciliary arteries. The arteria centralis relince is a very small branch which perforates the optic nerve, and is distributed to the interior of the eyeball. The dissection of these arteries will have in a measure effected the dissection of the muscles of the orbit. The Levator Palpebr^e is the most superficial of the orbi- tal muscles; it arises from the roof of the orbit in front of the optic foramen and is inserted by a broad tendon into the tarsal cartilage of the upper eyelid. This muscle is to be divided, and its two ends are to be reflected. Four straight muscles surround the optic nerve, and are named from their position superior and inferior, external and internal Recti Muscles ; with the exception of the external rectus they arise posteriorly from the circumference of the optic foramen and sheath of the optic nerve by a common attachment; the external rectus arises by two heads, the upper one joining the superior rectus, and the lower the inferior rectus, as well as the- lower border of the sphenoidal fissure; between these origins pass the motor oculi, (third,) the abducens, (sixth,) and the nasal branch of the ophthalmic nerve, to enter the orbit. The recti muscles are all inserted into the sclerotic coat of the eyeball, about a quarter of an inch from the cornea. The Superior Oblique Muscle is a small rounded muscle arising from the inner side of the optic foramen; it ends ante- riorly in a tendon which passes through a loop attached to the de- pression in the frontal bone at the inner part of the orbit, and is there reflected backwards and outwards, to be inserted into the sclerotic beneath the superior rectus muscle. From this pulley- like peculiarity the superior oblique is sometimes called the troch- learis muscle. The loop is a fibro-cartilaginous ring about an eighth of an inch in width, and lined with a synovial membrane. In order to examine the next muscle, the optic nerve and the recti muscles must be divided near their origin, and the eye gently turned out of its socket, so as to expose its inferior surface. 20 ANATOMY OF THE HEAD AND NECK. The Inferior Oblique Muscle arises from the superior maxillary bone, between the margin of the orbit and the lachrymal groove; it then passes across the orbit beneath the inferior and external recti, and is inserted into the sclerotic behind the inser- tion of the superior rectus. In dissecting the eye of a sheep, ox, or calf, the student is often puzzled by an additional muscle, of which he finds no descrip- tion. It is a suspensor or retractor of the eyeball, and, with the exception of man and the apes, appears to belong to all the mammalia; in most instances it is a quadrifid muscle, but in the ruminantia it coalesces into a single infundibuliform muscle, em- bracing the optic nerve, and attached anteriorly to the sclerotic, behind the cornea. DISSECTION IV. cranial nerves at their exit from the skull. Paragraphs marked with an asterisk can hardly be verified in an ordinary dis- section. We now proceed to examine the cranial nerves at their points of exit at the base of the skull. Soemmering counts these as twelve pairs, enumerating each nerve separately. Willis makes them but nine, including in one nerve all the trunks contained in the same aperture of the skull. The latter division is the one adopted. The cranial nerves, as they enter their foramina, are invested by a process of the dura mater, which constitutes a sheath for them; the pia mater also is prolonged upon them, but both mem- branes are soon lost in the surrounding tissues. The arachnoid is reflected backwards upon the internal surfaces of the cranial cavity. The First, or Olfactory Nerve, is soft and pulpy, and is often lost in the manipulation of removing the brain ; it lies upon the cribriform plate of the ethmoid bone, and towards its ex- tremity it assumes a bulbous shape; it sends a large number of CRANIAL NERVES AT THEIR EXIT FROM THE SKULL. 21 fine filaments, through the foramina of the bone beneath it, to supply the mucous membrane of the nares. The Second, or Optic Nerve, diverging from its commissure, as the conjunction between the two is called, enters the orbit through the optic foramen. This nerve is large and of a white color; it is accompanied by the ophthalmic artery, and invested with a firm sheath from the dura mater; it has no branches, and continues forward to the eyeball, at which it terminates in the retina. The orbital plate of the frontal bone, on the opposite side to that used for the dis- section of the muscles and arteries of the orbit, should be broken through with a chisel, in such a way as to make a triangular opening into that cavity, the base of which, an inch and a half wide, should be as far forwards as possible; the apex should lay bare the optic foramen, but without injuring the nerves. As the third and fourth nerves, and a branch of the fifth, lie in the walls of the cavernous sinus, the dura mater which constitutes it must be dissected away. The fifth nerve should also be cleared from the dura mater, and the Casscrian ganglion which lies upon the aj ex of the petrous portion of the temporal bone in the middle fossa, and into which the fifth nerve soon expands, should be dissected cleanly, and its two large trunks, the superior and inferior maxillary, traced to their points of exit, the foramina ovale and rotundum. The Third, or Motor Oculi Nerve, pierces the dura mater just in front of the posterior clinoid processes ; pursuing its course in the external wall o£ the cavernous sinus, it enters the orbit through the sphenoidal fissure, and divides into two branches. The superior branch supplies the superior rectus muscle and the levator palpebrae. The inferior branch supplies the in- ternal and inferior rectus and the inferior oblique. It will thus be seen that this nerve supplies all the muscles of the eye, ex- cept the external rectus and superior oblique, each of which has a special nerve. These branches are very small, and, lying in the midst of fat, require great patience and considerable skill to dissect. * The inferior branch of the motor oculi nerve sends a branch of communication to the lenticular ganglion, a small roundish body, the size of a pin's head, placed at the back part of the orbit, be- tween the optic nerve and external rectus muscle, and commonly on the outer side of the ophthalmic artery. This ganglion gives off the ciliary nerves, which pierce the sclerotic in company with the ciliary arteries around the optic nerve. The Fourth, or Trochleakis Nerve, is very small, and 22 ANATOMY OF THE HEAD AND NECK. sometimes puzzling to find. It pierces the dura mater close to the third nerve, and passes along the outer wall of the cavernous sinus to the sphenoidal fissure ; entering the orbit, it crosses the levator palpebra? at its origin, and supplies the trochlearis or su- perior oblique muscle. The Fifth, or Trifacial Nerve, the largest of the nine pairs of nerves, consists of two parts or roots. These two por- tions pass through the tentorium close to the apex of the petrous portion of the temporal bone; the larger division, immediately on reaching the middle fossa of the skull, expands into a flattened ganglion, the Casserian; the smaller division lies beneath the ganglion, and is only seen by turning it over. These two roots are distinct from each other, and the smaller one may be traced onwards to the inferior maxillary nerve. The Casserian ganglion gives off three branches—the ophthal- mic, and the superior, and inferior maxillary nerves. The ophthalmic nerve, arising from the upper portion of the ganglion, passes through the outer wall of the cavernous sinus, and enters the orbit through the sphenoidal fissure. It divides into three branches—nasal, frontal, and lachrymal. * The nasal passes between the two heads of the external rectus muscle, crosses the optic nerve, and enters the anterior «thmoidal foramen; it then reappears in the cranium at the side of the crista galli, and enters the nasal cavity, in front of the cribriform plate, to be distributed to the mucous membrane and integument of the nose. As the nasal nerve enters the orbit, it sends a branch to the lenticular ganglion. The frontal passes forwards upon the levator palpebral muscle to the supra-orbital foramen, where it emerges to supply the integument of the forehead. This nerve supplies a branch to the integument of the outer angle of the orbit, called the supra-trochlear branch. The lachrymal is the smallest of the three branches. It passes along the upper border of the external rectus muscle to the lachrymal gland and upper eyelid, to which it is distributed. The superior maxillary nerve, the second division of the fifth pair, passes out at the foramen rotundum, crosses the spheno-maxillary fissure, and enters the orbit by the canal in its floor, in company with the infra- orbital artery, one of the terminal branches of the internal maxillary; they both emerge at the infra-orbital foramen (p. 7), beneath the levator labii superioris muscle, and, forming a plexus with the facial nerve, supply the lower eyelid, upper lip, nose, and cheek. * This nerve gives off an orbitar branch, which, entering the orbit through the spheno-maxillary fissure, divides into two branches, which pass through CRANIAL NERVES AT THEIR EXIT FROM THE SKULL. 23 foramina in the malar bone, and are distributed to the temporal fossa, fore- head, and cheek. Dental branches also penetrate through small foramina in the tuberosity of the superior maxillary bone to the molar teeth, and from the infra-orbital canal through the lining membrane of the antrum to the anterior teeth. These branches, as well as that portion of the main trunk lying in the infra-orbital canal, cannot of course be seen without the removal of the eyeball. The inferior maxillary nerve is the longest of the three trunks into which the fifth pair divides; as it passes out through the foramen ovale it is joined by the second primary root of the fifth nerve, which lies behind the ganglion; it then divides into four branches, viz: muscular, the gusta- tory, the inferior dental, and the anterior auricular. The Sixth, or Abducens Nerve, pierces the dura mater on the clivus Blumenbachii of the sphenoid bone; it crosses the cavernous sinus, enters the orbit through the sphenoidal fissure, and passes between the two heads of the external rectus muscle, to which it is distributed. The Seventh Pair consists of two nerves, the Facial and Auditory; the facial is called the portio dura, the auditory the portio mollis, the former being of a dense, the latter of a soft and pulpy structure. Both of these nerves enter at the meatus audito- rius internus. In order properly to study these nerves, a temporal bone should be immersed in strong alcohol, and afterwards softened in hydrochloric acid; it can then be cut with a knife, and its canals followed out. The facial nerve is the smallest of the two trunks; after enter- ing the meatus auditorius, it passes through the aqueduct of Failo- pius and emerges at the stylo-mastoid foramen; it there divides into two branches, the temporo-facial and the cervico-facial; these have been already described (p. 11). Whilst in the aque- duct of Fallopius, this nerve forms a ganglionic enlargement, called the intumescentia gangliformis. A small branch of the Vidian nerve, which passes backwards beneath the Casserian ganglion, .enters the hiatus Fallopii to join the intumescentia; this is called the superficial petrosal nerve. * The auditory nerve enters the meatus auditorius, and dividing into two branches, the cochlear and vestibular, is distributed to the internal auditory apparatus. The Eighth Pair is composed of three nerves, the Glosso- 24 ANATOMY OF THE HEAD AND NECK. PHARYNGEAL, PnEUMOGASTRIC, and SPINAL ACCESSORY; these all pass out at the foramen lacerum posterius. * The glosso-pharyngeal nerve passes through a distinct canal of the dura mater in the foramen, and lies at its innermost extremity. That portion of the nerve lying in the jugular fossa presents two gangliform swellings, the superior being called the ganglion jugu- lare and the inferior the ganglion of Andersch. The existence of the ganglion jugulare is denied by some authors. The ganglion of Andersch gives off the tympanic, or Jacobson's nerve; this enters a small bony canal in the jugular fossa, and is distributed to the tympanum, forming the tympanic plexus, which communi- cates with the sympathetic and with the fifth pair of nerves. The glosso-pharyngeal nerve is distributed to the base of the tongue, the fauces, and the pharynx. * The pneumogastric or par vagum nerve passes out of the fora- men lacerum with the spinal accessory nerve ; it is the longest of the three nerves. In the foramen, it has a large ganglion called ganglion of the root, in contradistinction to the ganglion of the trunk, which is formed after it has escaped from the skull. * The spinal accessory nerve passes out of the foramen lacerum with the pneumogastric ; it has no ganglion. In the jugular fossa it divides into two branches, one of which joins the upper ganglion of the pneumogastric, and the other descends to the sterno-mas- toid muscle, which it perforates, and to which, with the trape- zius, it is distributed. The Ninth, or Hypoglossal Nerve consists of two bundles, which pass out at the anterior condyloid foramen by separate orifices of the dura mater. These unite after emerging from the skull, and the nerve is distributed to the muscles of the tongue. According to the arrangement which this book proposes, the subject is now to be turned over for the dissection of-the back: if the student has kept up with his companions, and accomplished the previous dissections, the turning may be done without incon- venience. The muscles of the back of the neck are given with those of the back, in Part Second, Dissection V. SUPERFICIAL CERVICAL REGION. 25 DISSECTION V. SUPERFICIAL CERVICAL REGION. The dissection is now transferred to the neck. The head should hang by its own weight, the chain hook should be caught into the septum of the nose, and by it the head should be rotated to one side, as far as it is possible to do so; this exposes rhe cervical region, and puts the muscles on the stretch. An incision is made along the median line, from the chin to the sternum, and another, if not already made, along the ramus of the jaw; a third is carried along the clavicle, from the termina- tion of the first, outwards. The skin is to be lifted from the angle at the sternum, but as the fibres of the platysma are often very thin and indistinct, and so pale in color as hardly to be distinguished from the fascia between it and the skin, this fascia must be raised with such care as to insure the demonstration of the muscle, however feebly it may be developed. The Platysma Myoides arises from the skin in front of the thorax, below the clavicle; its fibres ascend obliquely upwards and forwards, uniting upon the median line, when well devel- oped, with those of the other side, and are inserted into the symphysis of the chin, the angle of the mouth and the integu- ment of the face being intimately connected with, and in fact helping to form several of the muscles of the face. The platysma is to be removed without disturbing the fascia, or the numerous nerves that lie between it and the sterno-mastoid muscle. The removal of the platysma-myoides brings the cervical region more fairly into view. It will be seen that it is quadri- lateral, and that its boundaries may be indicated in a general way, as, superiorly, the ramus of the jaw and the mastoid process; inferiorly, the clavicle; posteriorly, the edge of the trapezius; and anteriorly, the median line of the neck. The cervical fascia varies in distinctness in different subjects ; it surrounds the neck, and is stronger in front of than behind the sterno-niastoid muscle, which it encases. The external jugular vein lies upon it, and perforates it at its lower part, and the branches of the anterior cervical plexus lie partly upon and partly beneath the fascia. The External Jugular Vein is formed by the union of the temporal, posterior auricular, facial, internal maxillary, and tem- poro-maxillary veins, veins of the integument and of the zygo- matic and pterygoid fossae. The external jugular vein is of variable size, and descends the neck, following a line from the 26 ANATOMY OF THE HEAD AND NECK. angle of the jaw to the middle of the clavicle, crossing the sterno- mastoid muscle, to penetrate the fascia, just at the side of the outer border of the clavicular portion of that muscle, and unite with the subclavian vein. In its course it is joined by the veins which accompany the supra-scapular and posterior scapular arteries in the posterior part of the neck. The anterior jugular vein, col- lecting the blood from the front of the neck, and descending along the anterior border of the sterno-mastoid, sometimes enters the external jugular, and sometimes passes beneath the sterno-mastoid, to join the internal jugular vein. The fascia is to be removed in dissecting the nervous branches which ramify in this region; for the most part these emerge behind the sterno-mastoid muscle, and are to be followed to their origin beneath it, so far as may be, without dividing it. The anterior branches of the four upper cervical nerves com- municate with each other by loops, and these loops, together with their branches, constitute the cervical plexus; it is covered in by the sterno-mastoid and platysma, and is distributed to the muscles and integument. Its branches are divided into ascending, de- scending, and deep. The ascending branches are three in number:— Superficialis colli, Auricularis magnus, Occipitalis minor. The superficialis colli nerre, coming from the second and third cervical nerves, emerges behind the posterior border of the sterno-mastoid, crosses it in a direction obliquely upwards, and divides into ascending and de- scending branches, which are distributed to the front of the neck. The auricularis magnus nerrt, likewise, comes from the second and third cervical nerves, and emerges at the posterior border of the sterno- mastoid, on the superficial surface of which it ascends, in company with the external jugular vein, to the parotid gland, where it divides into two branches, the anterior communicating with the facial, and giving • braaches to the external ear, parotid gland, and cheek; the posterior, crossing the mastoid process, supplies the back part of the external ear, the integument in the neighborhood, and communicates with the occipi- talis minor. The occipitalis minor nerve arises from the second cervical nerve, and is found lying upon the upper part of the posterior border of the sterno- mastoid muscle. It is distributed to the integument of the occipital region, and communicates with the occipitalis major, auricularis magnus, and posterior branches of the facial nerve. SUPERFICIAL CERVICAL REGION. 27 The descending branches of the cervical plexus come from the fourth cervical nerve, and are named acromial and clavicular, being distributed to the integument and muscles of the shoulder and anterior and upper part of the thorax. The deep branches will be described hereafter. The Sterno-mastoid Muscle is the large and prominent muscle which characterizes the cervical region; it is encased by the cervical fascia, and is crossed superficially by the external jugular vein and the branches of the cervical plexus. It arises by two heads, separated by an elongated interval; one, narrow, from the upper bone of the sternum; the other, broader, from the sternal third of the clavicle ; the extent of the clavicular attach- ment varies, and in some bodies may reach even to the trapezius. These two heads unite at about the middle of the neck in a round- ish belly, which is inserted into the mastoid process, and by a broad and thin aponeurosis into the superior curved line of the occipital bone. The Omo-hyoid Muscle is a small muscle which crosses the neck diagonally, in a direction crossing that of the sterno- mastoid, beneath which it lies; it is composed of two bellies, united in the middle by a tendon of variable length ; only one portion of the muscle can be well seen in the present stage of the dissection. It arises from the scapula at the outside of, and some- times in part from, the transverse ligament stretching across the supra-scapular notch; it then passes forwards, obscured from sight by the clavicle; behind the sterno-mastoid, the scapular por- tion terminates in a tendon which plays through a loop formed by the deep cervical fascia, this loop being attached to the cartilage of the first rib. From this intervening tendon commences another belly, which pursues a direction upwards and forwards, to be inserted into the hyoid bone at the point of union between its body and the greater cornu. Occasionally, one of the bellies of this muscle is wanting, and I have seen one case in which the whole muscle was absent on the right side. The sterno-mastoid and the omo-hyoid divide the quadrilateral cervical region into " triangles," convenient for purposes of sur- gical description; thus, the sterno-mastoid passing obliquely across the neck, that portion bounded by the median line in front, the jaw above and the sterno-mastoid behind, is called the great ante- rior triangle; that bounded by the sterno-mastoid in front, the 28 ANATOMY OF THE HEAD AND NECK. clavicle below and the trapezius posteriorly, the great posterior triangle. These triangles are each subdivided by the omo-hyoid muscle; the hyoid portion of which divides the anterior triangle, the space below it being called the inferior carotid triangle; that above it being again divided by the digastricus muscle into the superior carotid triangle and the submaxillary triangle. The scap- ular portion divides the posterior triangle into two smaller spaces, that above the belly of the muscle being called the occipital trian- gle and that below the subclavian triangle. The sterno-mastoid muscle may now be divided and its two ends reflected. In reflecting the upper half of the sterno-mastoid muscle its posterior surface should be examined for the spinal accessory nerve ; this nerve is one of the eighth pair of cranial nerves (p. 24); after emerging from the foramen lacerum posterius it be- comes connected by a branch of considerable size with the pneu- mogastric nerve and then continues onward to perforate the sterno- mastoid muscle at its under surface, after passing through which, and joining with branches of the cervical plexus in the occipital triangle, it is distributed to the trapezius muscle. It is presumed that the carotid artery has not yet been exposed, but that it still remains covered with its sheath. Its sheath is nothing but a portion of the deep cervical fascia which invests it together with the internal jugular vein. Upon this sheath may be seen a small nerve called the descendens noni; it is a branch from the hypoglossal, one of the cranial nerves, which will be found crossing the neck in a transverse direction just above the hyoid bone. The descendens noni forms a loop with a branch from the second or third nerve of the cervical plexus, called the communi- cans noni. The descendens noni is sometimes found within the sheath instead of upon it. Upon opening the sheath, the relation of the parts is to be care- fully observed. The artery and vein are separated from each other by a thin septum prolonged from the sheath. The vein is the internal jugular vein, and lies upon the outer side of the artery. Behind and between the artery and vein will be found the pneumogastric or par vagum nerve. Upon the inside of the artery the trachea will be seen, and between the trachea and artery a medium-sized nerve going to the larynx, and called the recurrent laryngeal. Between the artery and the SUPERFICIAL CERVICAL REGION. 29 transverse processes of the cervical vertebrae, on which it rests, may be found that part of the sympathetic nerve which connects the cervical ganglia. Some small branches of the sympathetic nerve, being cardiac branches, should also be noticed in connec- tion with this view of the parts. The artery is of large size and uniform calibre, and from its ori- gin until its division opposite the upper border of the thyroid carti- lage, gives off no branches, unless it be a very small twig, and is called the common carotid artery. Its course is indicated by a line drawn from the centre of the interval between the mastoid process and the angle of the jaw to the sterno-clavicular articulation ; this line corresponds to the anterior border of the sterno-mastoid muscle, which is called the guide to or the satellite of the artery. Having established these various connections, the dissection may be continued by the examination of the muscles placed over the trachea. The Sterno-hyoid Muscle lies at the side of the median line of the neck, being covered in at its lower part by the sterno- mastoid, and is a thin ribbon-like muscle about an inch in width, separated from its fellow of the other side by a slight cellular in- terval. It arises from the internal surface of the first bone of the sternum by a flat muscular origin, and is inserted into the lower border of the body of the hyoid bone. It is occasionally marked by transverse tendinous intersections. It lies upon the sterno- thyroid and thyro-hyoid muscles. The sterno-hyoid is to be divided and its two ends are to be reflected. The Sterno-thyroid Muscle arises also from the thoracic surface of the sternum, but lower down than the preceding : it is inserted into the oblique line of the thyroid cartilage of the larynx ; it is broader than the sterno-hyoid, and, like that, is occa- sionally marked by tendinous intersections. The Thyro-hyoid Muscle is a short muscle arising from the oblique line of the thyroid cartilage and inserted into the lower border of the body and cornu of the hyoid bone. The line of separation between this muscle and the sterno-thyroid is not always well marked; normally they are separated by a tendinous line at the point where they are attached to the oblique line of the thyroid cartilage, but it not unfrequently happens that even this is not sufficiently well marked to be apparent. 30 ANATOMY OF THE HEAD AND NECK. The sterno-thyroid muscle is to be divided, and its ends reflected, so as to expose the thyroid body. Between the carotid arteries and upon the trachea lies the Thyroid Body ; this is a dark red and vascular organ composed of two lobes, one on each side of the trachea, connected by a nar- row portion called the isthmus; these lobes are triangular in shape, the base being directed downwards. It is well supplied with arteries, receiving one from each carotid, the superior thy- roid going to the upper part of the body, and one from each thy- roid axis of the subclavian, called the inferior thyroid, and which supplies the lower part of the lobes ; occasionally there is a mid- dle thyroid artery sent to it from the innominata; all these arte- ries anastomose freely with each other. A small muscle called the levator glandula; thyroidece is sometimes found connected with the upper border of one lobe or the isthmus, and attached to the hyoid bone ; it is said to be most frequent in the left side, and its place is sometimes supplied by a small lobe of glandular tissue. DISSECTION VI. EXTERNAL CAROTID ARTERY. The dissection of the external carotid artery is now to be undertaken by follow- ing out from the main trunk those branches which have not been dissected in pre- paring the parts already described, and preserving those which have not yet been alluded to. Opposite the upper border of the thyroid cartilage or a little higher, the common carotid artery divides into two laro-e trunks, the external and internal carotid branches. At first, the external carotid lies upon the inner side, nearer the middle line of the body than the internal carotid, their distinctive names havino- reference, not to their relative position, but to their destination to parts nearer or more remote from the surface ; it soon, however, becomes superficial to the internal carotid and divides into nu- merous branches. The internal carotid may also be distinguished by a peculiar fusiform dilatation at its commencement; sometimes this dilatation is very marked, forming an abrupt rounded dis- tension of the vessel. EXTERNAL CAROTID ARTERY. 31 The external carotid is crossed by the stylo-hyoid and digas- tricus muscles, and by the hypoglossal nerve, and is imbedded for a part of its course in the parotid gland; between the angle of the jaw and the mastoid process it divides into the internal max- illary and temporal arteries. Its branches are Superior thyroid, Posterior auricular, Lingual, Ascending pharyngeal, Facial, Temporal, Occipital, Internal maxillary, The superior thyroid artery descends, passing beneath the omo-hyoid, sterno-rijyroid, and sterno-hyoid muscles to the thyroid body, to which it is distributed, and where it anastomoses with its fellow of the opposite side. It sends olfsets to the hyoid region and larynx, under the name of superior hyoid and inferior laryngeal branches. The lingual artery passes obliquely forwards beneath the hyo-glossus muscle. In that part of its course which is parallel to the os hyoides, the hyo-glossus muscle separates it from the hypoglossal nerve, the lat- ter being the more superficial. The lingual artery supplies the tongue, and is continued forwards to the tip of that organ under the name of the ranine artery. The facial artery arises above the lingual, sometimes from a com- mon trunk with it, and is directed upwards over the lower jaw to the face. It passes beneath the digastric and stylo-hyoid muscles and becomes im- bedded in the submaxillary gland. In its cervical portion it gives branches to the pharynx, tonsils, and submaxillary gland. The submental branch arises from the portion within the gland, and passes forwards upon the mylo-hyoideus muscle to the anterior belly of the digtstricus, where it terminates in branches, some of which turn upwards and reach nearly to the lower lip. Before crossing the jaw, which it does close to the anterior inferior angle of the masseter muscle, the facial artery is very tortuous, and continues so throughout the rest of its course (p 10). The occipital artery is a large artery destined to the posterior part of the head; it passes beneath the posterior belly of the digastricus, part of the parotid gland, and the sterno-mastoid; it crosses the jugular vein and the spinal accessory nerve, and the hypoglossal nerve curves around it near its origin. It gives off a small branch, the posterior meningeal, which ascends with the jugular vein through the foramen jugulare to the poste- rior fossa of the base of the skull. Near the middle line of the occipital bone the artery becomes superficial, and is distributed to the occiput, anas- tomosing with its fellow, with the posterior auricular and with the tempo- ral artery. A large but irregular branch, the princeps cervicis, descends the neck between the complexus and semi-spinalis colli and inosculates with the profunda cervicis, a branch of the subclavian. 32 ANATOMY OF THE HEAD AND NECK. The posterior auricular artery ascends between the ear and the occipital bone, and is distributed by two branches to the external ear and side of the head. This artery sends a small twig, called stylo-mastoid, through the stylo-mastoid foramen to the internal ear. The ascending pharyngeal artery arises at the point of bifurcation of the common carotid, and is very apt to be destroyed in the dissection. It is of small size, and ascends between the internal carotid and the pha- rynx. It divides into two branches, the meningeal, which enters the cra- nium through the foramen lacerum anterius, and is distributed to the membranes of the middle fossa of the skull, and the pharyngeal, which is distributed to the mucous membrane of the pharynx and the soft palate. The temporal artery is the terminal continuation of the external carotid; it passes up between the ear and the articulation of the jaw, through the substance of the parotid, and upon the temporal fascia divides into two branches which ramify on the front and the side of the head. This artery gives off parotidean branches to the parotid gland; the anterior auricular to the external ear; the transverse facial to the muscles of the face, cross- ing the cheek transversely beside Steno's duct, and anastomosing with branches of the facial (p. 10); the orbitar to anastomose with the palpe- bral arteries and the middle temporal, which perforates the temporal fascia just above the zygoma, and supplies the temporal muscle. The internal maxillary will be described hereafter. SUBMAXILLARY REGION. The dissection of the carotid artery will have also exposed and prepared a number of parts situated below .the inferior maxil- lary bone and between it and the hyoid bone. The Digastsiicus Muscle, lying above the hyoid bone and connected with it, is composed of two rounded bellies connected by a central tendon, the central tendon being the part attached to the hyoid bone ; these two bellies form an obtuse angle with each other; the posterior one arises from the digastric fossa of the temporal bone and is consequently covered in by the mastoid por- tion of the sterno-mastoid muscle and by the parotid gland. The anterior belly, closely connected though not united with the cor- responding part of the same muscle on the other side of the neck, arises from the side of the symphysis of the lower jaw; these two portions are attached by their central tendon to the body and greater cornu of the os hyoides. The tendon of the muscle is held in its place by a strong fascia and by fibres of the stylo-hyoid muscle which surround it. The posterior belly of this muscle crosses the carotid vessels, and along its lower border will be found SUBMAXILLARY REGION. 33 the occipital artery and the hypoglossal nerve. The facial nerve sends a branch to this muscle soon after its exit from the stylo- mastoid foramen. The Stylo-hyoid Muscle is in close connection with the preceding ; it arises from the styloid process of the temporal bone and passes down behind and to the inner side of the posterior belly of the digastricus ; at its lower part it splits, and allows the digastric tendon to pass through its substance; it is inserted in- to the os hyoides at the union of its body and cornu. It is some- times wanting. The facial nerve sends a branch to this muscle also, soon after it emerges from its foramen. The anterior belly of the digastricus is to be removed, and the submaxillary gland freed from extraneous cellular tissue, and loosened from its attachments. The Submaxillary Gland is a salivary gland, next in size to the parotid, which it resembles in general structure; it lies above the digastricus and upon the mylo-hyoid muscle ; it is partly concealed by the lower jaw, though it descends a variable distance down the neck; it is traversed by the facial artery, which sometimes is imbedded in it, and sends numerous small branches throughout its substance ; its duct, called Wharton's duct, may be seen issuing from its posterior part, and curving around the pos- terior border of the mylo-hyoid muscle, where it penetrates to open on the side of the frenum of the tongue. The gland is to be removed or drawn to one side. The Mylo-hyoid Muscle arises from the mylo-hyoid ridge of the inferior maxillary bone, and its posterior fibres pass for- wards to be inserted into the body of the os hyoides ; the anterior fibres join with those of the muscle of the other side, forming a sort of raphe" along the median line ; it is triangular in shape, and forms the floor of the mouth, the two muscles stretching across the interval between the two sides of the lower jaw. The mylo-hyoid branch of the inferior dental nerve ramifies upon its cutaneous surface, as well as a twig from tne internal maxillary artery, which accompanies that nerve. The submental branch of the facial artery also ramifies upon this muscle. The mylo-hyoid muscle is to be carefully removed or turned down towards the hyoid bone. The Genio-hyoid Muscle lies close to the median line, and arises from the inside of the symphysis of the lower jaw; it is 3 34 ANATOMY OF THE HEAD AND NECK. inserted into the centre of the body of the hyoid bone, in close apposition with the muscle of the other side, with which it is often united. If the submaxillary gland has been preserved, Wharton's duct may be seen resting upon the hyo-glossus muscle. The hypo- glossal nerve crosses that muscle, and in this part of its course gives off the descendens noni branch to the sheath of the carotid vessels (p. 28). By drawing the os hyoides downwards the gusta- tory branch of the inferior maxillary nerve will also be found resting upon the hyo-glossus muscle. The submaxillary ganglion, a small reddish body, is in close connection with the gustatory nerve, and lies just above the deep process of the submaxillary gland; it is extremely difficult to find. DISSECTION VII. PTERYGO-MAXILLARY REGION. The parts beneath the ramus of the jaw are of difficult dissection; and the num- erous important structures crowded into this limited space, are only with patience eliminated from their apparent confusion, or preserved in sufficient integrity to permit their examination. The zygoma having been already divided at its two ends, and, with the masseter, turned downwards, the next step is to saw through the interior maxillary bone below its neck, and again from the last molar tooth to just above its angle; this fragment, with the temporal muscle attached to the coronoid process, is then to be turned upwards, and both in refleoting it, and in sawing it through, the greatest caution is to be observed to divide nothing acciden- tally upon the inside of the bone; the internal maxillary artery and the inferior dental artery and nerve being in close apposition to it. After this piece of bone has been removed, and a little cellular tissue cleared away, the pterygoid muscles will appear, the external directed towards the condyle of the jaw, and the internal towards its angle. The coronoid process should be examined, to see the extent to which the temporal muscle is attached to its inner surface (p. 13). The External Pterygoid Muscle arises by two heads from the greater wing of the sphenoid bone, below the crest, and from the outer surface of the external pterygoid plate ; its fibres converge to be inserted in front of the neck of the lower jaw- bone; its separation into two heads is not always apparent; when present, the second head is inserted into the inter-articular fibro-cartilage of the temporo-maxillary articulation. The inter- nal maxillary artery rests upon this muscle. PTERYGO-MAXILLARY REGION. 35 The Internal Pterygoid Muscle arises from the ptery- goid fossa and from the inner surface of the external pterygoid plate, and is inserted into the angle and surface of the ramus of the jaw ; its fibres follow the same direction as those of the ma.— seter muscle externally, and from this, as well as from the corre- spondence of their insertions, it has sometimes been called the in- ternal masseter muscle. The condyle of the jaw, with the external pterygoid attached, is now to be dislo- cated and drawn forwards. The superior and inferior maxillary trunks of the fifth pair of cranial nerves will then be seen issuing from the skull; the former by the foramen rotundum, and crossing the spheno-max- illary fossa to the canal in the floor of the orbit; the latter by the foramen ovale, and dividing into two branches; the ante- rior one giving off five muscular branches to the masseter, buc- cinator, temporal, and external and internal pterygoid muscles; the posterior dividing into the auriculo-temporal, inferior dental, and gustatory branches. A branch from the internal maxillary artery accompanies each of the nerves sent to the above-named muscles. The otic, or Arnold's ganglion, should be sought for, resting upon the inner surface of the inferior maxillary nerve, just below the foramen ovale. The auriculo-temporal nerve, the terminal branches of which have been already dissected (p. 11), separates from the inferior maxillary near the skull; it passes outwards beneath the exter- nal pterygoid to the inner part of the articulation of the jaw, from which point it ascends with the temporal artery to ramify exter- nally upon the side of the head. The inferior dental nerve is the largest of the three trunks into which the inferior maxillary divides; it is at first beneath the external pterygoid muscle, afterwards it lies upon the internal pterygoid ; it then enters the inferior maxillary bone at the inferior dental foramen, to emerge at the mental foramen (p. 10), and supply the lower lip and chin; this nerve is accompanied by the inferior dental branch of the internal maxillary artery. Be- fore entering the canal in the bone, the inferior dental nerve gives off the mylo-hyoid branch, which, accompanied by the mylo- hyoid artery, a twig from the inferior dental, is continued along the inner aspect of the jaw to the mylo-hyoid muscle. 36 ANATOMY OF THE HEAD AND NECK. The gustatory nerve descends between the two pterygoid mus- cles to the side of the tongue, to the mucous membrane of which it is distributed ; its final distribution will be described with the dissection of the tongue. The small chorda tympani branch of the facial, arising within the temporal bone, and emerging from the fissura Glaseri, joins the gustatory nerve, and passing down in close apposition with it, establishes a connection with the submax- illary ganglion. The internal maxillary artery, one of the terminal branches of the external carotid, passes inwards behind the neck of the lower jaw, over the external pterygoid muscle to the spheno-max- illary fossa; it is very tortuous, and sends off a large number of small branches; these are the Masseteric, Inferior dental, Infra-orbital, Buccal, Tympanic, Pterygo-palatine, Temporal, (deep.) Meningea media, Spheno-palatine, External pterygoid, Meningea parva, Posterior palatine, Internal pterygoid, Superior dental, Vidian. The five muscular branches, the first named of the above list, and the inferior dental, have been seen in connection with corresponding branches of the anterior trunk of the inferior maxillary and the inferior dental nerves. These branches are all capable of demonstration. The meningea media branch ascends beneath the external pterygoid mus- cle, and enters the skull through the foramen spinosum of the sphenoid bone, to be distributed to the middle fossa of the cranial cavity. The meningea parva branch passes through the foramen ovale, the same at which the inferior maxillary nerve emerges, and is also distributed to the middle fossa of the skull. The superior dental branch, deeper seated than those yet described, de- scends in a tortuous manner upon the tuberosity of the superior maxillary bone, sending branches through small foramina to the teeth, the antrum and the mucous membrane of the gums. The infra-orbital branch is the terminal portion of the internal maxillary artery; from the spheno-maxillary fossa it enters the infra-orbital canal with the superior maxillary nerve, and emerges on the face at the infra- orbital foramen (p. 7). The remaining branches of the internal maxillary are of very small size, and, like the branches of the superior maxillary nerve, which they accompany, are incapable of demonstration, except by a special dissec- tion. The internal maxillary vein receives the veins corresponding PTERYGO-MAXILLARY REGION. 37 to the branches of the artery, and unites with the temporal vein in a trunk which is one of the principal in forming the external jugular vein ; the veins of the region form a plexus between the two pterygoid muscles. The Stylo-glossus Muscle will be found, as its name im- plies, arising from the apex of the styloid process of the temporal bone; it is crossed by the gustatory nerve, and is inserted into the side of the tongue. The Stylo-pharyngeus Muscle lies below the preced- ing ; it arises from the base of the styloid process, and is inserted into the pharynx and upper border of the thyroid cartilage; it passes between the carotid arteries, and the glosso-pharyngeal nerve turns over the lower part of its fleshy belly. Between the stylo-glossus and stylo-pharyngeus muscles is a fibrous band, connecting the tip of the styloid process and the lesser cornu of the os hyoides; it is called the stylo-hyoid liga- ment, and is sometimes cartilaginous, or even osseous, in a part or the whole of its extent. The styloid process is now to be cut through at its base, and with the two mus- cles just described turned downwards; the fascia surrounding the internal carotid and the internal jugular vein is to be removed without disturbing the nerves in contact with those vessels; they are the pneumogastric, glosso-pharyngeal, hy- poglossal, sympathetic, and spinal accessory. The Internal Jugular Vein is in close connection with, and upon the outer side of, the internal carotid artery ; it emerges from the skull at the foramen jugulare, as the continuation of the lateral and petrosal sinuses; at about the level of the os hyoides its size is considerably increased by the junction with it of the facial, lingual, thyroid, and occipital veins. This vein is some- times called the internal cephalic, between the skull and hyoid bone, and below that point the internal jugular. The Pneumogastric Nerve emerges from the jugular fora- men, and will be recognized by the ganglion (ganglion of the trunk) peculiar to it; this is nearly an inch in length, and sur- rounded by small nerves. The nerve lies between the jugular vein and internal carotid, and communicates with the hypoglossal, spinal accessory, and sympathetic nerves; it distributes branches to the parts about it, giving off & pharyngeal branch which unites with the glosso-pharyngeal nerve, and with which it forms a plexus 38 ANATOMY OF THE HEAD AND NECK. on the pharynx; the superior laryngeal branch, of considerable size, passes inside the internal carotid artery to the larynx, which it enters between the hyoid bone and thyroid cartilage, perforating the thyro-hyoid membrane; it also gives off cardiac branches, which unite with those of the sympathetic. The Glosso-pharyngeal Nerve also escapes from the jugular foramen, and should be traced up to its ganglion, the ganglion petrosum, which lies close to the bone, and from which emanate the branches which unite this with the other nerves. This nerve crosses over the internal carotid to the lower border of the stylo-pharyngeus muscle ; it there assumes an almost trans- verse direction to the pharynx, and finally passes under the hyo- glossus muscle, being distributed to the pharynx, tongue, and tonsil. The Spinal accessory Nerve, blending with the trunk of the pneumogastric, issues from the foramen jugulare, and is con- nected by small branches with the other nerves of this region. It passes outwards either over or under the jugular vein, to perfo- rate the sterno-mastoid muscle at its upper part, and, uniting with the anterior cervical plexus,-is distributed to the trapezius. The Internal Carotid Artery ascends vertically from the upper border of the thyroid cartilage to the base of the skull; the rectus capitis anticus major muscle separates it from the ver- tebrae ; excepting at its commencement, where it has a fusiform dilatation, it maintains the same size throughout, and gives off no branches; it enters the carotid canal of the temporal bone to emerge in the cranial cavity for the supply of the orbit and the encephalon. This vessel may be tortuous instead of straight. The ascending pharyngeal artery, seen in this dissection, is a branch of the external carotid, given off just as the common caro- tid bifurcates. It ascends between the internal carotid and the pharynx upon the spinal column ; it gives a branch to the pha- rynx, and near the skull, where it becomes tortuous, it sends a branch through the foramen lacerum to supply the middle fossa' of the skull. The Hypoglossal Nerve lies deep beneath the internal carotid ; it issues from the skull at the anterior condyloid fora- men, passes between the vein and artery, and descends to curve round the occipital artery, and become superficial at the lower PTERYGO-MAXILLARY REGION. 39 border of the posterior belly of the digastricus muscle, from whence it is directed forwards to the tongue and its muscles. The Sympathetic Nerve in the neck consists of a gangli- ated cord, which lies close to the spinal column; it is connected with a similar gangliated cord in the thorax, and with several ganglionic bodies in the head in connection with the three trunks of the fifth nerve. The cervical portion of the sympathetic has three ganglia; the superior one is fusiform in shape, and an inch or more in length ; it is placed on the rectus capitis anticus major muscle, beneath the internal carotid artery and the trunks of the eighth nerve, which must be raised to expose it. It is connected with the other nerves, spinal as well as cranial, by minute branches; some of these, called nervi molles, ramify on the trunks of the carotid, and form plexuses on their subdivisions. It sends a branch downwards behind the sheath of the carotid to the heart, called the superior cardiac nerve. The middle cervical ganglion is situated opposite the fifth cer- vical vertebra, on or near the inferior thyroid artery, whence it is sometimes called the thyroid ganglion ; it is of a roundish shape, and gives off branches to connect with the spinal nerves, and to ramify upon the thyroid artery ; it also gives off the middle car- diac nerve, which descends to the thorax, crossing the subclavian artery, and terminating in the cardiac plexus. The middle gang- lion is sometimes wanting. The inferior cervical ganglion occupies the interval between the first rib and the transverse process of the first cervical verte- bra, and will be seen in a later stage of the dissection. DISSECTION VIII. The upper portion of the sternum should now be removed, with the sternal half of the clavicle Attached, and the ribs cut away on each side as far as the insertions of the scaleni muscles; this will expose the deep vessels of the neck in their rela- tion to the heart; the cellular tissue which covers them is to be carefully removed by following the vessels downwards from the point at which they are already dis- sected in the neck. The sterno-clavicular articulation should, however, be first examined, and this may be done before it is detached from the thorax. 40 ANATOMY OF THE HEAD AND NECK. STERNO-CLAVICULAR ARTICULATION. The internal extremity of the clavicle is strongly connected with the upper bone of the sternum by several ligaments. The capsular ligament surrounds the joint, being attached to the bones near the articulating surfaces. The inter-clavicular ligament is a strong rounded cord, inter- vening between the superior surfaces of the two clavicles, and closely attached to the incisura semilunaris of the sternum. The costo-clavicular ligament is a band passing obliquely for- wards from the under surface of the clavicle at its sternal end, to the cartilage of the first rib; sometimes the clavicle touches the rib, and has an articular surface at this point; the subclavius muscle lies in front of this ligament. The inter-articular fibro-cartilage will be seen on dividing these ligaments and detaching the clavicle ; it is nearly circular in form, and thicker in the centre than at the circumference ; it is adherent by its edges to the ligaments which surround the articulation. Its sternal surface is much more convex than its clavicular, which is nearly flat, and corresponds to a concavity in the sternum, so that the articulation in reality is between the sternum and the fibro-cartilage, and not between the sternum and clavicle. The inter-articular cartilage divides the joint into two separate parts, each provided with a separate synovial membrane. BASE OF THE NECK. At the root of the neck the parts exposed will exhibit first the great venous branches which return the blood from the head and upper extremity. The internal jugular vein descends the neck on the outer side of the carotid artery, and enters the subclavian vein, which is the continuation of the axillary vein ; according to Struthers, the in- ternal jugular vein at this point is provided with two valves. The Subclavian Vein lies in front of the artery of that name, and the union of this with the preceding vein forms the Vena Innominata. The vena innominata is further reinforced by the vertebral vein, which descends with the vertebral artery through the foramina of the transverse processes of the cervical vertebrae, and by the inferior thyroid veins, coming from the BASE OF THE NECK. 41 thyroid body and its neighborhood. The two venae innomi- nate unite to form the Superior Vena Cava, and, owing to the destination of that vessel to the right auricle, the vena innomi- nata of the left side is considerably longer than that of the right, and its direction more nearly transverse ; it lies upon the three primary trunks of the aorta, and upon the upper part of the arch itself. The thoracic duct enters the left innominata vein at its commencement; the precise point may be demonstrated by in- flating the duct in the thorax with a blow-pipe. The ductus lym- phaticus dexter, which is the termination of the lymphatic vessels of the right side of the head and neck, right arm, and right side of the thorax, enters the right innominata vein near its commence- ment. The orifices of both these lymphatic ducts are provided with sigmoid valves to prevent the admission of blood. Between the subclavian vein and artery may be traced the pneumogastric and phrenic nerves. The pneumogastric nerve we have already seen higher in the neck, lying between the carotid artery and internal jugular vein (p. 87) ; its lower part is now to be observed. It follows a course a little different on one side from that of the other; on the right side the nerve passes in front of the subclavian artery, between it and the vein ; on the left side it passes down between the left subclavian and common carotid, and then crosses the arch of the aorta; below these points they resemble each other in their course, which is behind the root of the lung, along the oeso- phagus, to the stomach. As the right pneumogastric crosses the subclavian, it gives off the recurrent laryngeal branch which curves around that vessel, and is reflected upwards to the larynx; on the left side this branch is given oft" as the nerve crosses the aorta, and it curves around this at the point where the ductus arteriosus is obliterated, to ascend like the other. In their course upwards the recurrent branches lie on the inner side of the carotids, be- tween the oesophagus and the trachea, to both of which they give branches ; they terminate by filaments distributed to all the mus- cles of the larynx except the crico-thyroid, which is supplied by the superior laryngeal nerve. The Phrenic Nerve is a medium-sized nerve arisingfrom the anterior trunks of the third and fourth cervical nerves, and occa- sionally from the fifth; it descends obliquely upon the anterior 42 ANATOMY OF THE HEAD AND NECK. scalenus muscle, crossing from its outer to its inner edge, and enters the thorax in front of the subclavian artery, but behind its vein, to pass down in front of the root of the lung upon the pericardium to the diaphragm, to which it is distributed. The Arch of the Aorta gives rise to three vessels; the in- nominata, the left carotid, and the subclavian ; the number is sometimes increased by the left vertebral, which in a certain number of cases arises from the aorta, instead of from the left subclavian ; when this irregularity takes place the supernumerary vessel is usually given off between the carotid and subclavian arteries. Occasionally, the number of primary branches is re- duced to two. A very slight interval separates the aortic trunks from each other. The Innominata Artery is a short trunk, three quarters of an inch in length ; it lies upon the trachea, which it crosses somewhat obliquely, and then divides into the right carotid and right subclavian arteries. The innominata occasionally gives off a branch called the middle thyroid, which ascends tortuously in front of the trachea to the thyroid body ; the existence of this anomalous branch, it will at once be seen, might essentially cofn- plicate the operation of tracheotomy. The Common Carotid Arteries will be seen to have a dif- ferent origin, the right being from the innominata and the left directly from the aorta ; the right is consequently shorter than the left by the length of the innominata. Separated at first only by the width of the trachea, they diverge as they ascend, their relations, excepting at their origin, being the same on the two sides. The right carotid occasionally arises directly from the aorta. The Subclavian Artery differs, not only in origin, but in direction, on the two sides of the bod}', the right comino- from the innominata and the left from the aorta direct; the rio-ht, more- over, is shorter than the left by the length of the innominata. The left subclavian ascends horizontally, and then turning sud- denly, forms a right or an obtuse angle, whilst the right describes a gradual and regular curve. On both sides the artery passes beneath the scalenus anticus muscle, and rests upon the first rib which is slightly grooved at the point where it reposes. The sca- lenus separates the artery from its vein, which passes alone in BASE OF THE NECK. 43 front; behind the artery are the scalenus posticus muscle, and the branches of the brachial plexus of nerves, which in a measure sur- round it. At the lower border of the first rib the subclavian be- comes the axillary artery. The right subclavian has been observed to spring from the aorta as a separate trunk, and in such cases is most frequently the last in order of the primary aortic trunks ; in such a case it crosses the neck obliquely in front of the vertebral column and beneath the oesophagus to regain its usual position. The left subclavian may arise in common with the left carotid. At this period of the dissection should be observed the variable height to which the pleural cavity sometimes extends above the first rib ; a prolongation of two or three inches having been ob- served a number of times, by C. E. Isaacs. It will be seen that when such is the case, the thoracic cavity might easily be opened in the course of any operation in this locality. The subclavian artery gives origin to the following branches, viz: Vertebral, Internal Mammary, Thyroid Axis, Superior Intercostal. The vertebral artery, the first and largest of the branches, ascends the neck upon the transverse processes of the vertebra; until it reaches the sixth, when it penetrates the vertebral foramen and follows the canal formed by these as far as the atlas; having passed through the foramen of this, it curves around its articulating process, perforates the dura mater and enters the foramen magnum to unite with the vertebral of the other side in forming the basilar artery. In the canal it lies in front of the an- terior trunks of the cervical nerves, except the first and second, the for- mer of which it crosses on its inner, the latter on its outer side. In its course the vertebral artery gives off branches to the membranes of the spinal cord and the deep muscles of the cervical region, and a posterior meningeal branch to the posterior fossa of the cranial cavity and falx cerebelii. Occasionally this artery does not enter the vertebral canal till it has reached a point higher than the sixth vertebra. The arteries of the two sides may vary in size, in which case it is ordinarily the left which is largest; one of them may also, as has been stated, arise from the aorta; this irregularity has rarely, however, been noticed except on the left side. The thyroid axis springs from the subclavian, close to the inner side of the scalenus anticus muscle; it does not always exist, as the branches to which it gives rise are not unfrequently given off directly from the sub- clavian ; they are 44 ANATOMY OF THE HEAD AND NECK. Inferior thyroid, Supra-scapular, Transversalis cervicis. The inferior thyroid artery, a vessel of considerable size, passes obliquely inwards, behind the common carotid, to the thyroid body, which it pene- trates at its posterior surface, and in the substance of which it anastomoses with its fellow of the opposite side, and with the superior thyroid, a de- scending branch from the external carotid; in its course it supplies a branch called anterior cervical to the posterior aspect of the trachea. The place of this artery is sometimes taken by a trunk called the middle or lowest thyroid, or thyroid of Neubauer, and which comes from the innominata or aorta, ascending in front of the trachea to the lower part of the thyroid body. This branch may be present also without the absence of the infe- rior thyroid. The supra-scapular artery is a large branch which passes outwards, behind the clavicle, to the scapula, where crossing the supra-scapular notch, it is distributed to the dorsum of the scapula, as is described in Part Second, Dissection VI. The transversalis cervicis artery, also a large branch, crosses the neck higher than the preceding and divides into two branches, the superficialis cervicis, distributed to the under surface of the trapezius muscle, and the posterior scapular, which passes beneath the levator anguli scapulae and turns downwards along the base of the scapula, as is described in Part Second, Dissection V. The posterior scapular sometimes arises as a sepa- rate trunk from the subclavian, and it may be outside of the scalenus muscle; in this case the transversalis cervicis is of small size. The superior intercostal artery is a descending branch of the subclavian, and can only be got at satisfactorily by cutting away the ribs in front; it turns over the neck of the first rib and supplies two, and occasionally three of the upper intercostal spaces. The profunda cervicis artery usually arises in common with the preced- ing branch, although it may arise independently from the subclavian; it passes between the transverse processes of the seventh cervical and first dorsal vertebrae, and ascends the neck between the complexus and semi- spinalis colli muscles, to anastomose with the descending branch of the occipital artery called princeps cervicis. (See Part Second, Dissection V.) .The inferior cervical ganglion, the third of the cervical ganglia of the sympathetic nerve (p. 39), lies behind the superior inter- costal artery in the interval between the first rib and the trans- verse process of the seventh cervical vertebra. It is the largest of the three and irregularly rounded in shape ; it is united with the middle cervical ganglion and with the chain of ganglia in the thorax. It gives off the inferior cardiac nerve, which lies beneath the subclavian artery, and after joining the recurrent laryngeal BASE OF THE NECK. 45 branch of the pneumogastric is continued to the deep cardiac plexus behind the aorta. The internal mammary artery is a large descending branch given off from the subclavian, and although occasionally arising from the thyroid axis, or in common with the sub-scapular, is very constant in its mode of origin; it is distributed to the inner surface of the anterior portion of the thorax, and is described in Part Second, Dissection III. The Brachial Plexus can be better examined as to its ori- gin and plan of formation at this period of the dissection than in connection with the axilla. It is formed by the union of the an- terior branches of the last four cervical and first dorsal nerves; the fifth and sixth nerves emerging from the inter-vertebral foramina descend obliquely to unite in a trunk which speedily bifurcates; the first dorsal and eighth cervical ascend obliquely to unite in a large trunk which also bifurcates; the seventh continues by itself as far as the first rib, and then bifurcates to join one branch with the lower bifurcation resulting from the union of the fifth and sixth nerves, and its other branch with the upper bifurcation resulting from the union of the first dorsal and eighth cervical nerves. We thus have four branches represent- ing five original trunks. DISSECTION IX. The section known in the French amphitheatres as the coupe du pharynx is now to be made. The trachea and oesophagus, being divided opposite the top of the sternum, are to be turned up over the face; the chisel is to be applied at the apex of the triangle formed by the upper part of these and the vertebral column, and keeping it close to the latter, the basilar process is to be broken through behind the sella turcica: the skull is then to be separated into two halves, one anterior and the other posterior, by a section of the saw carried behind the styloid process and di- rected iuwards and a little forwards; the two sides should be sawed separately and the two incisions should meet where the basilar process has been cut through with the chisel; the occiput and vertebral column will then constitute one of the pieces, whilst the other will be made up of the face, tongue, trachea, and pharynx. Upon the latter of these pieces, the student should examine the lips, to see the frenum formed by the mucous membrane and attaching them to the lower and upper jaws on the median line. The orifice of Steno's duct, in the cheek (p. 12), near the 46 ANATOMY OF THE HEAD AND NECK. second molar tooth of the upper jaw, should also be sought and explored by probing. The lips and cheeks may then be removed from the bones, and the articulation of the lower jaw dissected on that side which has not been destroyed by the examina- tion of the pterygo-maxillary region. articulation of the lower jaw. In the Temporo-maxillary Articulation, the condyle of the lower jaw is received into the glenoid fossa of the temporal bone. The external lateral ligament is a short, stout band of fibres, passing obliquely backwards from the tubercle of the zygoma to the outer side of the neck of the lower jaw. The internal lateral ligament is a membranous expansion from the spinous process of the sphenoid bone to the margin of the dental foramen; the internal maxillary artery passes between this ligament and the jaw. The stylo-maxillary ligament extends from the styloid process to the angle of the jaw. These two latter hardly merit the name of ligaments, as they in no way serve to consolidate the articulation; the first being but a protection to the vessels, and the second a surface of origin of the stylo-glossus muscle. The inter-articular fibro-cartilage is seen on opening the joint; it is elliptical and bi-concave in shape, and sometimes perforated in the centre: externally it is attached to the external lateral liga- ment, and internally to the external pterygoid muscle. Two synovial membranes are present, one above and the other below the inter-articular cartilage. pharynx. The lower jaw should be removed, excepting about half an inch on each side of the symphysis. The pharynx should be stuffed with tow, cotton-wool, or like material; and, when thus distended, the constrictor muscles will be easily dis- sected. The constrictor muscles are three in number, and are so arranged that the lower overlaps the middle, and the middle the upper muscle; they are attached superiorly by an aponeurotic expansion connected with the base of the skull, and anteriorly to the larynx, hyoid bone, tongue, and bones of the nasal cavity. BASE OF THE NECK. 47 The Constrictor Inferior is the most superficial of the three; it arises from the side of the cricoid cartilage, and from the oblique line and upper and lower borders of the ala of the thyroid cartilage; from this origin the fibres are directed back- wards in a radiated manner, and are inserted along the posterior median line of the pharynx, into a raphe with the corresponding muscle of the other side; the lower fibres are continuous with the muscular fibres of the oesophagus. The recurrent laryngeal nerve passes under its lower border. The Constrictor Medius arises from the greater cornu of the os hyoides, and from the stylo-hyoid ligament; its fibres radi- ate from this origin, and blend along the middle line with the muscle of the other side, ending at its upper border in the apo- neurosis of the pharynx. The glosso-pharyngeal nerve passes under the upper border of this muscle, and the stylo-pharyngeus muscle separates it from the superior constrictor. The stylo-pharyngeus muscle, already described (p. 37), is again seen in this connection, arising from the base of the styloid pro- cess, and descending between the superior and middle constrictor, to be inserted partly into the pharynx, and partly into the upper border of the thyroid cartilage. The stylo-hyoid ligament, already described (p. 37), is again seen extending from the tip of the styloidprocess to the lesser cornu of the os hyoides. The Constrictor Superior arises from the inner surface of the internal pterygoid plate, from the pterygo-maxillary liga- ment, the mucous membrane of the side of the mouth, and from the posterior part of the mylo-hyoid ridge of the lower jaw; from this extensive and irregular origin its fibres pass backwards, and are inserted into the pharyngeal aponeurosis. The portion arising from the mucous membrane of the mouth has been de- scribed as a separate muscle called glosso-pharyngeus. The pterygo-maxillary ligament is the raphe of union which ex- ists between the superior constrictor and the buccinator muscle, one extremity being attached to the hamular process of the inter- nal pterygoid plate, and the other to the extremity of the molar ridge of the lower jaw. The pharyngeal aponeurosis connects the muscular part of the pharynx with the base of the skull, being attached superiorly to 48 ANATOMY OF THE HEAD AND NECK. the basilar process of the occipital bone and the petrous portion of the temporal bone,- and inferiorly losing itself in the muscular strata of the pharynx. The pharynx is now to be laid open along the posterior median line; it is also to be dissected away, for a short distance on each side from its aponeurotic attachment to the occipital bone. The pharynx terminates in the oesophagus by a constriction opposite the cricoid cartilage. The mucous membrane of the pharynx is thicker, redder, and more abundantly supplied with muciparous glands than that of the oesophagus. The section of the pharynx exposes the posterior apertures of the nasal cavity, divided by the septum nasi. On each side of this will be found the trumpet-shaped orifice of the Eustachian tube; if the mucous membrane is removed from the orifice, it will be found that this tube is composed of cartilage, and is nearly an inch in length; it is attached superiorly to a groove between the sphenoid and the petrous portion of the temporal bone, through which it communicates with the cavity of the tympanum. A bundle of muscular fibres extending from the lower border of the Eustachian tube to the palato-pharyngeus muscle, may some- times be found; it is called the salpingo-pharyngeus muscle; it does not always exist. palatine region. The Isthmus Faucium is the constriction between the mouth and the upper part of the pharynx, formed above by the soft palate, and below by the tongue. The Soft Palate is a dependent structure which intervenes between the mouth and the palate ; it is continuous with the roof of the mouth superiorly; inferiorly its border is free, and from its centre hangs a pendulous body called the uvula. Two folds spring from each side of the uvula, and are continued downwards on the sides of the isthmus faucium; these are the arches or pil- lars of the palate, the anterior one reaching the side of the tongue at its root, and the posterior being continuous with the side of the pharynx. Between these pillars lies the tonsil. The Tonsil is a collection of mucous follicles, forming a body rounded in shape, but variable in size; the apertures of the follicles are sometimes very apparent; it is placed just above otic and Meckel's ganglia. 49 the tongue, and corresponds with the angle of the jaw exter- nally. The muscles of the palate are difficult of dissection, on account of their small size, and their close connection with surrounding parts. The upper attachment of the pharynx, with the superior constrictor, must be removed; the mucous mem- brane of the posterior surface of the soft palate is to be raised with great care, so as not to injure the muscular or tendinous fibres which compose the greater part of its substance; it may be made tense for dissection by drawing down and fastening the uvula by a hook or pin. The Levator Palati arises from the under surface of the apex of the petrous portion of the temporal bone< and from the cartilage of the Eustachian tube ; it then passes down by the side of the posterior nares, and spreads out in the structure of the soft palate as far as the median line. The Tensor Palati arises from the scaphoid fossa at the base of the pterygoid plate, and from the outer part of the Eus- tachian tube; it terminates in a tendon which winds round the hamular process of the pterygoid plate, and is inserted into about half an inch of the posterior border of the palate bone, and into the aponeurosis of the soft palate, underneath the tendon of the preceding muscle. The Palato-pharyngeus Muscle forms the posterior pil- lar of the soft palate; it arises by a broad expansion from the lower part of the soft palate, and is inserted into the posterior border of the thyroid cartilage. The Azygos Uvulae is situated along the posterior surface of the middle line of the soft palate, and consists of two bundles of very pale fibres arising from the spine at the posterior border of the hard palate, and terminating at the free extremity of the uvula. The Palato-glossus Muscle, or Constrictor isthmi Faucium, forms the projection of the anterior pillar of the soft palate; it arises from the aponeurosis of the soft palate in front of the tensor palati, and is inserted into the lateral surface and dorsum of the tongue. otic and Meckel's ganglia. The tongue, hyoid bone, and larynx, may now be separated from the portion of the skull to which they were attached, and reserved for further examination. The spheno-maxillary fossa is to be searched for certain ganglia of the sympathetic system. 4 50 ANATOMY OF THE HEAD AND NECK. The Otic or Arnold's Ganglion, if not already examined in connection with the inferior maxillary nerve, will be found as a small ovoid body just below the foramen ovale, on the inner side of the inferior maxillary nerve, and at the point where it is joined by the second root of the trifacial nerve. This ganglion gives branches to the tensor tympani and tensor palati muscles, communicates with the nerves of its vicinity, and sends a branch to the Vidian nerve, called nervus petrosus superficial minor; but its connections are by twigs so minute that their examination can only be accomplished by the aid of a lens and by a special dissection. In the spheno-maxillary fossa, and connected by short branches with the superior maxillary nerve, is the spheno-palatine, or Meck- el's ganglion ; it lies below the superior maxillary nerve, above the posterior palatine canal, and outside the spheno-palatine fora- men ; its branches are directed upwards to the orbit, downwards to the mouth, inwards to the nose, and backwards to the pharynx and Vidian canal. The large palatine branch passes through the posterior palatine canal forwards on the roof of the mouth to the incisor teeth, where it unites with the naso-palatine branch of the same ganglion. The naso-palatine branch crosses the roof of the nasal fossa to the sep- tum nasi, on the side of which it descends to the anterior palatine canal, ,i where it unites with the large palatine branch. The Vidian nerve passes through the Vidian or pterygoid canal, then en- ters the cranium through the cartilaginous substance closing the foramen '. lacerum anterius, and lying in a groove on the surface of the petrous portion of the temporal bone, takes the name of nervus petrosus superfi- cial major, and enters the hiatus Fallopii to join the gangliform enlarge- ment of the facial nerve. These branches can hardly be found except by a special dissection, <■ Before discarding the piece of bone which the student has just been examining, he should open the carotid canal to see the tern- ; poral portion of the internal carotid artery. The canal can be \ opened by bone forceps, or a small chisel carefully handled. \ The artery at first ascends, is then directed forwards horizontally, ' and lastly turns upwards into the cranium opposite the foramen .1 lacerum. In the canal it is surrounded by branches from the *1 superior cervical ganglion of the sympathetic nerve ; it gives off m a minute branch to the tympanum. fl TONGUE. 51 NASAL FOSSiE. To expose the nasal cavities, the saw should be placed at the side of the crista galli, and carried through the nasal and frontal bones to the roof of the mouth; this separates the portion of skull into two halves, leaving the septum nasi at- tached upon one side. The two cavities on either side of the septum are called nasal fossa; they communicate with the pharynx and face by aper- tures, called anterior and posterior nares, and also with the sinuses of the frontal, ethmoid, sphenoid, and superior maxillary bones. The septum of the fossae is partly osseous and partly car- tilaginous, being formed by the perpendicular plate of the eth- moid, the vomer, and the triangular cartilage of the nose. The septum is usually more or less bent to one or the other side. On the outer boundary of the nasal fossae will be found the three convoluted spongy or turbinated bones. The two superior are processes of the ethmoid bone; the lower one is an indepen- dent bone, called the inferior turbinated bone. These bones over- hang spaces called meatuses; they are three in number; the superior meatus is the smallest, and occupies about the posterior half of the outer boundary of the nasal fossa; the posterior eth- moidal sinuses open into it in front, and in the dried bone at its posterior part is the spheno-palatine foramen, by which the nerves and vessels enter the nose. The middle meatus reaches nearly the whole length of the outer wall; it communicates anteriorly with the frontal sinuses and anterior ethmoidal cells, and near its middle is a small oblique aperture the size of a crow's quill, which leads to the cavity of the antrum. The inferior meatus also reaches the whole length of the nasal fossa; at its anterior part is the opening of the lachrymal duct, and on a level with, but be- hind it, the Eustachian tube may be seen. The mucous membrane which Tines the fossae and meatuses is continuous with the skin anteriorly, and the pharyngeal mucous membrane posteriorly, and is called the pituitary or Schneiderian membrane. DISSECTION X. TONGUE. The Tongue is made up of muscular fibres, interspersed with fat and cellular tissue, and enveloped by mucous membrane • by 52 ANATOMY OF THE HEAD AND NECK. its base it is attached to the hyoid bone; anteriorly by a fold of mucous membrane, called frenum linguce, to the symphysis of the lower jaw, and posteriorly to the epiglottis, by a central and two lateral folds of mucous membrane, called frenum epiglottidis. On each side of the frenum linguae is a papilla, which marks the orifice of the Whartonian ducts (p. 33). On each side of the frenum there is also a prominence caused by the sublingual gland; this is a flattened and elongated conglomerate gland, similar to the other salivary glands, but smaller; it pours its secretion into the mouth by numerous small orifices, called Rivinian ducts, which open on each side of the frenum. The upper surface of the tongue is covered with numerous papillae, called from their shape conical and filiform; the latter are most numerous along its sides; scattered amongst these are some larger papillae, which from being larger at the top than at the base are hence called fungiform. At the base of the tongue, arranged across it in the shape of the letter V, are eight or ten papillae called caliciform ; they are pedunculated, and surrounded by a fold of mucous membrane ; at the apex of the two rows of these papillae is a deep mucous follicle, called the foramen caecum. Some of the muscles of the tongue have been already described and divided; their lingual ending may be further followed out, and the intrinsic muscles dissected by removing the mucous membrane; to do this the tongue should be fixed by large pins driven through it, to the table on which it lies. The Hyo-glossus Muscle arises from the great cornu and body of the os hyoides, and is inserted beneath the stylo-glossus into the side of the tongue. That portion of the muscle arising from the body of the hyoid bone, passes obliquely backwards, and has been called the basio-glossus. That from the great cornu passes forwards, and has been called the cerato-glossus; whilst a few fibres from the lesser cornu, spreading along the side of the tongue, have been named the chondro-glossus. These names were applied to the different parts of the muscle by Albinus. The ex- istence of the chondro-glossus is disputed. Between the hyo-glossus and the genio-hyo-glossus, and con- nected with that portion of the hyo-glossus described as the chon- dro-glossus, is a bundle of fibres running longitudinally from the base to the apex of the tongue ; this is called the inferior lingualis. LARYNX. 53 The superior lingualis is a thinner and less distinct band of fibres just beneath the mucous membrane on the dorsum of the tongue arising from the frenum epiglottidis, and extending forwards to its apex. The hyo-glossus must be divided at its hyoid attachment, and reflected, in order to expose the next muscle. The Genio-hyo-glossus Muscle is triangular in shape; it arises from the symphysis of the lower jaw, beneath the genio- hyoid, and expanding fan-shaped, is inserted into the whole length of the tongue and into the body of the hyoid bone ; by making a longitudinal section of the tongue in the median line, the direction of its fibres will be plainly visible. . A section thus made will also show the fibrous septum which separates the tongue into two halves, giving to it the character of duality which belongs to all the special senses; although rudi- mentary in the human species, the separation into two parts is marked in the tongues of certain birds and reptiles. The lingual artery will be found resting upon the genio-hyo- glossus muscle; it gives a branch to the dorsum of the tongue, and is continued forwards to its apex under the name of the ranine artery; it lies close to the muscular fibres. Upon the hyo-glossus muscle the gustatory nerve will be seen ; this is a branch of the inferior maxillary trunk of the third nerve; it anastomoses with small branches of the hypoglossal, and is distributed to the mucous membrane and papillae of the tongue. The hypoglossal nerve also crosses the hyo-glossus muscle, and after penetrating the genio-hyo-glossus, is continued forwards to the apex of the tongue in the substance of that muscle. It is supplied to the muscular structure of the tongue. The glosso-pharyngeal nerve passes under the posterior border of the hyo-glossus muscle, and is supplied to the dorsum and lateral mucous membrane of the tongue, and to the tonsils and fauces. LARYNX. The tongue should now be separated from the larynx without injuring the epiglottis; the hyoid bone should remain attached to the larynx. The larynx should be extended, and made fast to the table by means of pins; the pharynx and extrinsic muscles should be dissected away from its cartilages and from the hyoid bona. 54 ANATOMY OF THE HEAD AND NECK. The hyoid bone is connected with the thyroid cartilage of the larynx by a membrane called the thyro-hyoid membrane, which includes the entire space intervening between the upper border of the thyroid cartilage and the upper border of the hyoid bone; this membrane is perforated by the superior laryngeal nerve and the superior laryngeal artery. The Crico-thyroideus Muscle is a triangular muscle, and the largest of the special muscles of the larynx; it arises from the front and lateral part of the cricoid cartilage, and passes out- wards and backwards, to be inserted into the ala of the thyroid cartilage. The Crico-arytenoideus posticus Muscle arises from the depression on the side of the vertical ridge of the cricoid cartilage posteriorly, and is inserted into the base of the outer angle of the arytenoid cartilage. The Arytenoideus Muscle is placed in the concavity of the posterior surface of the arytenoid cartilages; the fibres of this muscle consist of fasciculi, which cross each other in an oblique direction. To expose the remaining muscles of the larynx, one side of the thyroid cartilage must be removed. The Crico-arytenoideus lateralis Muscle will be found arising from the lateral part of the upper border of the cricoid cartilage, and inserted into the outer angle of the base of the arytenoid cartilages, in connection with the next muscle. The TnYRO-ARYTExoiDEUS Muscle arises from the thyroid cartilace, near the middle line, and from the crico-thyroid mem- brane, and is inserted into the base' and outer surface of the arytenoid cartilage- By its outer surface this muscle rests upon the thyroid cartilage ; by its inner surface, it is in contact with the vocal chords and the ventricle of the larynx. The Depressor Epiglottidis lies in the fold of mucous membrane, between the epiglottis, and the arytenoid cartilage; it is a thin muscular layer, arising from the front and upper part of the arytenoid cartilage, and inserted into the border of the epiglot- tis. Some of the lower fibres of this muscle have received the name of Mr. Hilton, and been described by him as the compressor sacculi laryngis. The cavity of the larynx is divided into two parts, by a con- LARYNX. 55 striction caused by the prominence of the thyro-arytenoid liga- ments ; these are two elastic bands attached, in front, to the re- ceding angle of the thyroid cartilage, and, posteriorly, to the base of the arytenoid. The superior ligament is the smallest; the inferior one is called the chorda vocalis. The space between the two ligaments of either side is called the rima glottidis, and that between the two ligaments on the same side the ventricle of the larynx. In' the ventricle of the larynx the mucous membrane forms a deep pouch, best demonstrated by stuffing with pellets of cotton-wool; this is called the sacculus laryngis, and is directed upwards, sometimes as high as the upper border of the thyroid cartilage. The larynx is supplied with nerves from the superior and infe- rior laryngeal branches of the pneumogastric nerve. The superior laryngeal penetrates the thyro-hyoid membrane, and supplies the mucous membrane. The inferior or recurrent laryngeal passes beneath the ala of the thyroid cartilage, and supplies all the special muscles of the larynx except the crico-thyroid, which has a separate branch from the superior laryngeal nerve. These nerves are accompanied by the laryngeal branches of the superior and inferior thyroid arteries, which accompany them in their distribution to the mucous membrane and muscles. The hyoid bone and the cartilages of the larynx are now to be denuded, care being taken to leave the ligaments uniting the different cartilages and the membrane between the larynx and hyoid bone. The Hyoid Bone consists of a body and four cornua, two creater and two lesser. The greater cornua extend backwards, decreasing gradually in size, and ending posteriorly in a tuber- cle; the lesser corn u is directed upwards, and is about the size and shape of a kernel of rice; it marks the union of the body of the bone with the greater cornu, and is seldom co-ossified with it; the stylo-hyoid ligament is attached to it. The Thyroid Cartilage of the larynx consists of two square halves united in the median line, where they form a projection called pomum Adami; posteriorly it has a thick border, which terminates above and below in a cornu; the upper being the longest, and the lower the stoutest. The upper cornu is con- nected to the greater cornu of the hyoid bone by a ligament, called thyro-hyoid; a sesamoid bone, or cartilage, is usually found in it. 56 ANATOMY OF THE HEAD AND NECK. The lower cornu articulates with the cricoid cartilage. The inner surface of this cartilage is smooth, the outer is marked by an oblique ridge, extending from the superior cornu to the middle of the lower border. This cartilage is connected to the cricoid by a membrane called the crico-thyroid. The Cricoid Cartilage forms a complete ring, and is thicker than the thyroid ; it is broader behind than in front, and resem- bles somewhat in its shape a signet ring; the inner surface is smooth, the outer is rough for the attachment of muscles; the lower border is straight, and united by a fibrous membrane with the first ring of the trachea ; the upper border is irregular. The Arytenoid Cartilages are two in number, one on each side, and are placed on the upper border of the cricoid cartilage at the back of the larynx; they are pyramidal in shape. Attached to the apex of each of these is a small fibro- cartilaginous body, called the cartilage of Santorini. The Cuneiform Cartilages are attached to the middle 6f the external surface of the arytenoid cartilages ; they are some- times wanting. The Epiglottis is composed of yellow elastic fibre, and re- sembles in shape a rounded leaf with the stalk downwards; it is connected with the tongue by the frenum epiglottidis, and by a fibrous band to the notch in the anterior border of the thyroid cartilage below; it is also connected with the hyoid bone by strong bands of fibrous tissue. Between the epiglottis and the hyoid bone is a mass of yellowish fat, which has been erroneously called the epiglottidean gland. The Trachea is composed of from sixteen to twenty incom- plete cartilaginous rings, each forming about three fourths of a circle ; sometimes they blend together, but for the most part are united by a fibrous tissue, which also extends across between their ends posteriorly, to complete the tube. The posterior wall of the trachea, besides this fibrous membrane, consists of mus- cular fibije closely connected with the mucous membrane beneath, and its surface is dotted with well-marked muciparous glands, the ducts of which pass forwards to the mucous membrane. The continuation of the trachea is described in connection with the lungs. PREVERTEBRAL REGION. 57 DISSECTION XI. PREVERTEBRAL REGION. The dissection now reverts to that portion of the vertebral column put aside after the separation of the pharynx, and we proceed to examine the prevertebral region. The removal of a small amount of cellular tissue exposes several muscles; the su- perior ones of which, the rectus capitis anticus major and minor, are usually found mutilated by the cutting through of the occipital bone. The Rectus Capitis anticus major Muscle, superiorly the most superficial of the prevertebral muscles, arises by tendinous slips from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae ; these unite to form a single belly, and the muscle is inserted into the basilar pro- cess of the occipital bone. The Longus Colli Muscle, partly concealed by the pre- ceding, is, however, superficial at its lower part, where it lies upon the bodies of the vertebras. This muscle is pointed above and broad below, and consists of an external and an internal part, the former being vertical, and the latter oblique. The internal part arises by fleshy and tendinous processes from the bodies of the two upper dorsal and two lower cervical vertebrae ; the external part from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae; the two parts then blend together, and are inserted by four slips into the lower border of the bodies of the four upper cervical vertebrae ; some of the- most external fibres of the lower part of this muscle are occasionally attached by separate tendons to the transverse pro- cesses of the lower cervical vertebras. The Rectus Capitis anticus minor Muscle lies beneath the rectus anticus major, which must therefore be removed; it arises from the anterior border of the lateral half of the atlas, and is inserted into the basilar process of the occipital bone. The Rectus Capitis lateralis Muscle arises from the transverse process of the atlas, and is inserted into the rough surface of the occipital bone external to its condyle. The Scalenus Anticus Muscle arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebra?, and is inserted into a tubercle on the upper surface of the first rib; this tubercle is important to notice, , 58 ANATOMY OF THE HEAD AND NECK. as being the guide for the finger in searching for the subclavian artery when that vessel is to be tied. The vertebral origin, it will be observed, corresponds with that of the rectus anticus major muscle, of which it may in some sort be considered the con- tinuation. The Scalenus medius Muscle arises from the posterior tubercles of all the transverse processes of the cervical vertebrae, except the first, and is inserted by two fleshy bellies into the first and second ribs, the one inserted into the second being smaller than that into the first rib; the attachment to the second rib is often described as a separate muscle, under the name of scalenus posticus. Between the anterior tubercles of the transverse processes of the cervical vertebrae, are the anterior pairs of the inter-lrans- versales muscles, the first pair being between the atlas and axis, and the last between the last cervical and first dorsal vertebra. The lower anterior inter-transversalis muscle is often wanting. Between the pairs, except in the first two spaces, the anterior primary branch of the cervical nerves makes its exit; beneath the posterior muscle the other primary branch of the same nerve emerges. The anterior division of the first spinal or sub-occipital nerve, is given off from the common trunk whilst the latter lies upon the posterior arch of the atlas ; it then curves downwards in front of the transverse process of the atlas, and forms a loop of communi- cation with an ascending branch of the second cervical nerve ; it supplies the rectus lateralis and anticus minor, and communicates with the pneumogastric, hypoglossal, and sympathetic nerve. The anterior division of the second cervical nerve, passes over the lamina of the axis, is directed forwards, outside the vertebral artery, and beneath the inter-transverse muscle of the,first space, to join the cervical plexus. The vertebral artery, described at p. 43, may now be further examined, by removing the inter-transversales muscles ; it will then be seen lying in the canal of the transverse processes of all the cervical vertebrae, except the seventh; after einer small bundle of nervous filaments lies between these two nerves, and is called the interme- diate portion of Wrisberg; it unites with the" auditory nerve. The Eighth Nerve consists of three trunks, the Glosso-pha- 68 ANATOMY OF THE HEAD AND NECK. ryngeal, the Pneumogastric, and the Spinal Accessory; they are all placed along the side of the medulla oblongata. The glosso-pharyngeal nerve is the smallest of the three, and arises by three or more filaments, springing from the lateral tract, close to the facial nerve. The pneumogastric, or par vagum nerve, arises below the pre- ceding, also from the lateral tract, by a series of filaments which are finally gathered into a flat band. The spinal accessory nerve consists of two parts, one being accessory to the pneumogastric and the other spinal. The ac- cessory part arises by minute filaments in a line with the pneumo- gastric, as low as the first cervical nerve; this portion does not unite with the pneumogastric till it gets outside the skull. The spinal part is a round cord arising by filaments froni the spinal cord, as low down as the sixth cervical nerve. The glosso- pharyngeal, pneumogastric, and spinal accessory nerves converge and meet just below the crus cerebelli. The Ninth, or Hypoglossal Nerve, arises by a series of fil- aments from the sulcus, between the pyramidal and olivary bodies of the medulla oblongata, in a line with the anterior roots of the spinal nerves. MEDULLA OBLONGATA AND PONS VAROLII. The Medulla Oblongata is the upper enlarged portion of the spinal cord. Its shape is pyramidal and its length about an inch and a quarter; its base is limited by the transverse fibres of the pons Varolii, but its apex blends with the cord and is not as definitely marked. The anterior surface is convex, the posterior is somewhat concave and forms the floor of the fourth ventricle. It is divided into halves by a median longitudinal fissure in front and behind, the anterior one ceasing at the pons in a dilated part called the foramen ccecum; the posterior is prolonged into the floor of the fourth ventricle. Each half of the medulla is made up from the three lateral divisions of the spinal cord, indications of which still exist, though they are somewhat differently arranged and changed in form. That portion nearest the longitudinal fis- sure in front, is called the anterior pyramid or corpus pyramidale ; at about an inch below the pons the pyramids of the two sides communicate across the anterior fissure by what is called a decus- BASE OF THE CEREBRUM. 69 saiion of their fibres. The anterior pyramids are the continua- tion upwards of the anterior columns of the spinal cord. Next the anterior pyramids comes the corpus olivare. This is an oval projection, separated by a groove on each side from the anterior pyramids in front, and the restiform body behind ; its upper end is the most prominent and does not quite reach the pons; its lower end is characterized by some transverse fibres arching over its surface, and called arciform fibres. That part of the medulla below the olivary body is continuous with the lateral column of the spinal cord, and is here sometimes called the lateral tract; its fibres are continued upwards, much diminished in size, between the olivary and restiform bodies. On each side of the posterior longitudinal fissure is the corpus restiforme. This is the largest prominence of the medulla, and by its lateral projection gives width to its upper part. The posterior pyramids are placed on each side of the longitudinal fissure, lower down than the resti- form bodies, and are the continuation upwards of the posterior columns of the spinal cord ; at the lower part of the medulla they diverge and become blended with the restiform bodies. The Pons Varolii is situated above the medulla oblongata and between the hemispheres of the cerebellum; it is of a square shape, the anterior border arching over the crura cerebri, and the posterior over the prolongation of the medulla. The super- ficial fibres of the pons are transverse and collect together on each side to form the crura cerebelli; the deep fibres are longitu- dinal and are prolonged from the medulla. The crus cerebri is a large stalk-like body emerging from the anterior border and dip- ping into each lateral hemisphere of the cerebrum ; as it enters the hemisphere it is crossed transversely by the optic tract. BASE OF THE CEREBRUM. Between the crura cerebri on each side and the optic commis- sure in front is the inter-peduncular space, containing the locus perforatus, the corpora albicantia, and the tuber cinereum. The locus perforatus, sometimes called thepons Tarini, is a layer of whitish-gray substance, between the corpora albicantia in front, and the pons Varolii, behind. It gets its name from being perfo- rated by numerous arterial twigs, intended for the interior of the brain. 70 ANATOMY OF THE HEAD AND NECK. The corpora albicantia are two small round bodies, placed just behind the optic commissure ; they are the termination of the crura of the fornix. The tuber cinereum is a mass of gray matter between the cor- pora albicantia and the optic commissure ; projecting from it is a small conical body called the infundibulum, which is connected with the pituitary body. The pituitary body lies in the sella turcica, and has been exam- ined in connection with the base of the skull (p. 17). If the two hemispheres of the brain be gently parted, the cor- pus callosum will be seen; this is the broad transverse band which unites the two hemispheres of the brain; it has a rounded border in front, called its genu, from which it extends back- wards under the name of the rostrum, forming a concave margin, to which is joined a thin layer of gray substance, called lamina cinerea, which unites posteriorly with the tuber cinereum. The corpus callosum will be farther examined in connection with the interior of the brain. The fissure of Sylvius is the separation of the anterior and middle lobes ; externally the fissure divides into two parts one of which passes before and the other behind a cluster of convolutions called the island of Reil. At the inner extremity of the fissure is a triangular spot, called substantia perforata, from being pierced by a number of openings for small arteries; its inner side is con- tinuous with the lamina cinerea. UPPER SURFACE AND INTERIOR OF THE CEREBRUM. The brain is to be turned over so as to bring its convexity uppermost; a roll of cloth should support the whole, and e!evate the anterior lobes so as to bring them on a level wiih ihe posterior. The two hemispheres are separated by a median longitudinal fissure, at the bottom of which will be seen the broad white band of the corpus callosum, interrupting the fissure at its central part but leaving the separation of the hemispheres complete both in front and behind it. The superficies of the hemispheres is marked by tortuous eminences called gyri, or convolutions, and by intervening depressions called sulci. Some of these convolutions have been named, as, for instance, that at the bottom of the me- dian fissure, where the hemisphere rests upon the corpus callo- UPPER SURFACE AND INTERIOR OF THE CEREBRUM. 71 sum, which is called the convolution of the corpus callosum or gyrus fornicatus. The hemispheres of the cerebrum sometimes present a want of symmetry as to size; Bichat believed this to be a condition inconsistent with a perfect performance of the functions of the brain : no more striking proof of the incorrect- ness of such a view can be found than the fact that the brain of Bichat himself presented this very peculiarity. The upper part of each liemisphere is lo be cut off by a horizontal section as low as the convo'ution of the corpus callosum. The section thus made will show that each convolution consists, superficially, of a layer of grayish-colored cerebral substance, lying upon a whiter structure constituting the central portion of the section ; the gray matter is called cortical,.and the white me- dullary. If a single hemisphere has been cut through, the medul- lary matter of that side will be seen to have an oval shape called centrum ovale minus; if both have been cut through a larger me- dullary surface is exposed, and the two ovals will be found to con- stitute one large oval, to which the name centrum ovale majus is given ; and the surface of which, in a recent brain, is dotted with minute bloody points resulting from the division of small vessels. The Corpus Callosum is the great commissure of the brain. It is about four inches in length; its fibres are transverse and marked along the central line by a raphe'; if the convolution called gyrus fornicatus be cut through transversely, and turned forwards and backwards, a white, longitudinal band of fibres will be exposed, called the stria; longitudinales laterales, or covered band of Reil. In front, the corpus callosum bends round to the base of the brain, the bend being called its genu; posteriorly it forms a thick rounded border; on each side it forms the roof of the cavities in the hemispheres called the lateral ventricles, and, by its under surface, is connected with the septum lucidum anteriorly and with the fornix posteriorly. The ventricles of the brain are cavities which exist in its inte- rior ; they are five in number. One is found in the central part of each hemisphere; these are called lateral ventricles, and con- stitute the first and second; the third occupies the middle line of the brain near its under surface; the fourth is between the cere- bellum and the posterior surface of the medulla oblongata and 72 ANATOMY OF THE HEAD AND NECK. pons Varolii; the fifth is in the partition that separates the two lateral ventricles from each other. The lateral ventricle of either side is displayed by shaving off as much of the cor- pus callosum and central medullary substance of each hemisphere as constitutes its roof; the escape of a fluid which is ordinarily present, warns the dissector of his arrival in the cavity of the ventricle. The Lateral Ventricle is a narrow interval extending into the anterior, middle, and posterior lobes of the hemisphere by three prolongations called cornua ; the anterior cornu is directed outwards ; the posterior, which is small, turns inwards, and the descending, middle or inferior cornu penetrates in a spiral manner into the middle lobe. This ventricle presents from before back- wards the following parts for examination, viz :— Corpus striatum, Hippocampus major, Taenia semicircularis, Hippocampus minor, Optic thalamus, Septum lucidum, Choroid plexus, Fornix. The corpus striatum, a large pear-shaped body in the anterior part of the lateral ventricle, is so called from the striated lines of white and gray matter which are seen upon cutting into its sub- stance. The broad end directed forwards is separated by the septum lucidum from its fellow of the opposite side; its narrow end projects backwards outside the optic thalamus. The taenia semicircularis is a narrow band of longitudinal fibres, lying between the corpus striatum and the optic thalamus ; in front it joins the pillar of the fornix, and posteriorly is lost in the descending cornu of the ventricle. The optic thalamus is an oblong body, a part of the upper surface of which is alone seen, the rest being covered by the for- nix ; its posterior portion projects into the descending cornu of the ventricle; its further relations will be subsequently exam- ined. The choroid plexus is a vascular fringe formed from the pia mater, which extends obliquely across the ventricle ; posteriorly it penetrates into the descending cornu, and anteriorly it commu- nicates with the plexus of the other side through the foramen of Monro, which may be demonstrated by pulling the plexus gently with a pair of forceps, whilst the septum lucidum is held aside with the handle of a scalpel. UPPER SURFACE AND INTERIOR OF THE CEREBRUM. 73 The hippocampus major is the projection which lies at the commencement of the descending cornu, behind the choroid plexus; it follows the direction of the cornu, and its extremity has been likened to the foot of an animal, the two or three inden- tations which are found upon it having been named pes hippo- campi. In order to see this, the cornu must be laid open by a careful division of the external wall of the hemisphere, following a direction backwards, outwards, and downwards, and then for- wards and inwards. The primary letters of these terms, used to express the curve taken by the cornu, have given rise to a mne- monic symbol, Bodfi, by which the student may with ease remember its course. The hippocampus minor is the projection which occupies nearly all the space of the posterior cornu. The corpus callosum is to be cut through transversely at its middle; the ante- rior half is to be raised by separating it from the fornix, and reflected forwards; this exposes the septum lucidum and its ventricle. The posterior half is to be raised, and reflected backwards; the fornix will thus be exposed. The septum lucidum is a thin, triangular, and almost transparent partition between the lateral ventricles; it consists of two layers, inclosing a space, which is the fifth ventricle. The septum luci- dum is so delicate a structure, that if the decomposition of the brain has at all advanced, it will only be seen as it tears away during the gentle lifting of the anterior portion of the corpus callosum, to the under surface of which it is attached superiorly ; its lower border corresponds to the rostrum, and its apex to the genu of the corpus callosum; its base is applied to the fornix as it arches downwards in front. The fornix is a thin, horizontal stratum, attached along the median line of the corpus callosum, behind the septum lucidum; in front it arches over the foramen of Monro, to form on either side crura, which terminate in the corpora albicantia and optic thalami; posteriorly it sends off on each side an expansion called its posterior pillars, which lie along the hippocampus major. It is this part of the fornix which is seen in the floor of the lateral ven- tricle when first laid open, and the thin edge of which, concealed by the choroid plexus, is called corpus fimbriatum or tcenia hip- pocampi. If the fornix be divided anteriorly and reflected back- wards, we shall see upon its under surface, between its diverging, 74 ANATOMY OF THE HEAD AND NECK. posterior pillars, a triangular space marked by transverse lines, and called the lyra. The reflection of the fornix exposes the optic thalami, and it will be seen that it rests upon and covers in these bodies in nearly their whole extent. If we follow the for- nix by its free edge or taenia hippocampi into the descending cornu of the ventricle, we shall find, on lifting it from the optic thalamus, that there is a fissure extending downwards to the ex- tremity of the cornu, and forwards to the foramen of Monro, through which an expansion of the pia mater enters the ventricle, and forms the fringed margin called the choroid plexus; the ven- tricle being made a closed cavity by the reflection of its lining membrane on to the pia mater, where it passes through this fis- sure. This fissure is named the transverse fissure of the cere- brum, or fissure of Bichat. The central part of the pia mater which thus enters the ventri- cles, lying beneath the fornix, and corresponding to it in shape and extent, is called the velum interpositum ; its upper surface is in contact with the fornix, and its margin laterally is the choroid plexus; its under surface is the roof of the third ventricle, and it covers the pineal body and a part of each optic thalamus. The velum is traversed along its median line by two veins called vence Galeni, which, commencing at the foramen of Monro, terminate posteriorly at the straight sinus. The velum interpositum is now to be raised and thrown backwards. It must be done with care not to injure the parts beneath. On the under surface of the velum are the choroid plexuses of the third ventricle ; continuous in front by the foramen of Monro with the plexus choroides of the lateral ventricle, which they resemble in their structure, they are connected posteriorly with the pineal gland, and this connection is to be remembered in removing the velum, or that body may be torn away with it. The Third Ventricle is an interval between the optic thalami; its roof is the velum interpositum, and its floor the inter- peduncular space at the base of the brain ; in its anterior portion are the descending crura of the fornix and the anterior commis- sure ; in its posterior the pineal gland and posterior commissure, covering in the corpora quadrigemina. On its two sides we have the optic thalami, and, crossing from one to the other of these, the middle or soft commissure. UPPER SURFACE AND INTERIOR OF THE CEREBRUM. 75 The anterior commissure is a round bundle of white fibres, sit- uated just in front of the crura of the fornix, which must be sepa- rated in order to display it; it crosses between the corpora striata. The middle or soft commissure, frequently torn across in exam- ining the brain, consists of gray matter, and connects the adjacent sides of the optic thalami. The posterior commissure is a flattened white band, connecting the optic thalami posteriorly. The space between the anterior and middle commissures is called the foramen commune anterius, or foramen of Monro, and is the medium of communication between the lateral and third ventricles, and of the transmission of the choroid plexuses and their termination, the venae Galeni. This foramen is also called the iter ad infundibulum, from leading down to the funnel-shaped cavity of the infundibulum. The space between the middle and posterior commissures is called the. foramen commune posterius; it is the point from which a canal, called the aqueduct of Sylvius on iter a tertio ad quartum ver- triculum, leads backwards through the base of the corpora quadri- gemina to the fourth ventricle, completing the intercommunication existing between all the ventricles. The two lateral ventricles communicate with each other transversely, and with the third per- pendicularly, through the foramen of Monro, and we have just seen how the third and fourth ventricles are connected. It is a disputed point whether the fifth ventricle communicates with the third ; if it does, it is by a very narrow orifice at the angle formed by the inferior and posterior borders of the septum lucidum. The weight of authority is against the existence of any aperture at that point. The optic thalamus is a square-shaped body forming part of both the lateral and the third ventricles; it forms a large part of the descending cornu of the former, where it presents two rounded tubercles called corpus geniculatum externum and internum, and is in relation externally with the corpus striatum and substance of the hemispheres. Anteriorly the thalami are connected with the crura of the fornix as they descend to the corpora albicantia, and posteriorly they are joined by bands from the pineal body and the corpora quadrigemina. 76 ANATOMY OF THE HEAD AND NECK. The pineal body is a small conical mass of a reddish color and vascular character, situated above, and by its base connected with, the posterior commissure and between the anterior pairs of the corpora quadrigemina ; it is also connected with the optic thalami by white bands called its peduncles. The pineal body is hollowed out into a cavity containing, besides a viscid fluid, a quantity of gritty matter called acervulus, easily demonstrated by rubbing it between the fingers. The pineal body was supposed by Des- cartes to be the seat of the soul. The corpora quadrigemina are four small, rounded protuber- ances arranged in pairs and separated by grooves; each pair is situated on the crus cerebri of the same side. The anterior pair, called nates, are the largest; they are oblong in shape and send forwards a white band to join the optic thalami. The posterior pair, called testes, are rounder and whiter than the preceding, and are also connected with the thalami by a white band. The iter a tertio ad quarlum ventriculum passes longitudinally through the base of the corpora quadrigemina. By drawing back the cerebellum two large white cords will be seen extending from the corpora quadrigemina to the cerebellum; these are the processus e cerebello ad testes or superior peduncles of the cerebellum. Between these is stretched a thin layer of cere- bral substance, overlaying the passage from the third to the fourth ventricle, and covering in a part of the fourth ventricle it- self; this is the valve of Vieussens. CEREBELLUM. The cerebellum is to be detached from the remains of the cerebrum by carrying the knife through the optic thalami, so that the cerebellum, with the corpora quadrigemina, pons Varolii, crura cerebri, and medulla oblongata, shall all remain united together. The Cerebellum, or little brain, lies beneath the posterior lobes of the cerebrum, from which, in the cranial cavity, it is sep- arated by the tentorium ; its diameter is greatest from side to side, and it is incompletely divided into two lateral hemispheres. Its surface is marked by plates or lamina; instead of convolutions, and between these are fissures lined by pia mater ; the deeper of these fissures break the hemispheres into imperfectly marked lobes. CEREBELLUM. 77 The two hemispheres are united on the upper or cerebral as- pect by a central, constricted isthmus, called the superior vermi- form process; in front of this is a notch which encircles the cor- pora quadrigemina posteriorly, called incisura cerebelli anterior; behind the isthmus is another notch called incisura cerebelli posterior. Upon the under surface of the cerebellum the depres- sion which receives the medulla oblongata is called the vallecula, and at the bottom of this is an isthmus, corresponding to that connecting the hemispheres on the superior surface, and called the inferior vermiform process. The cerebellum is united to the rest of the encephalon by a large stalk-like process on each side. This process subdivides into three rounded cords, called peduncles. The superior pe- duncle, or processus e cerebello ad testes, is directed forwards to the corpora quadrigemina, and forms the anterior part of the lateral boundary of the fourth ventricle ; between the peduncles is the valve of Vieussens. The middle peduncle, or processus ad pon- tem, is commonly called the crus cerebelli and is the largest of the three peduncles. Its fibres begin in the lateral part of the cerebel- lum, and are directed forwards to the pons Varolii, of which they form the transverse fibres, uniting with the fibres of the crus of the opposite side. The inferior peduncle, or processus ad medul- lam, passes downwards to the medulla oblongata and forms part of the restiform body ; it is also the inferior portion of the lateral boundary of the fourth ventricle. The Fourth Ventricle is a space between the cerebellum and the posterior aspect of the medulla oblongata and pons Va- rolii ; it has the shape of a lozenge, the points of which are di- rected upwards and downwards, the upper extending as high as the superior border of the pons and the lower to a level with the inferior part of the olivary body. The lower half of this space has been called calamus scriptorius, from a fancied re- semblance to the tip of a writing pen ; its lateral boundaries are formed by the superior peduncles of the cerebellum above, and by the restiform bodies below; its roof by the valve of Vieussens and the sides of the peduncles with which it is connected, and by the under part of the superior vermiform process; its floor corre- sponds to the posterior surfaces of the medulla and pons. Along the centre of its floor is a median groove, ending at the point of the 78 ANATOMY OF THE HEAD AND NECK. calamus, and on each side of the groove a fusiform elevation called eminentia teres. The eminentia teres is crossed by some white streaks, varying in their arrangement and not always recognizable, called linece transversa. The fourth ventricle communicates with the third ventricle through the itera tertio ad quartum ventriculum, and by this canal the lining membrane of the other ventricles is prolonged into the fourth. The arachnoid and pia mater stretch across between the me- dulla oblongata and cerebellum, at the lower part of the ventricle, under the name of the valve of the arachnoid. On the inner sur- face of these membranes is a vascular fold, called the choroid plexus of the fourth ventricle. The ventricles communicate with the sub-arachnoid space of the encephalon and spinal cord) through an aperture in this membrane just above the calamus. A vertical section of the cerebellum shows that the laminae of its hemispheres are composed of an external layer of gray matter and an internal layer of white medullary substance, the white part being derived from a large medullary centre in the interior of each hemisphere, which in one direction gives rise to the pe- duncles of the cerebellum, and in the other, diverging like the branches of a tree, enters by small offsets into each lamina; the appearance thus presented is called arbor vitce cerebelli. A portion of the medullary centre of the cerebellum will be found inclosed by a waved or dentated gray line ; this is called the corpus rhomboideum, and a similar appearance, bearing the same name, may be found in the olivary body of the medulla, on slicing it obliquely in its long diameter. By dividing transversely one of the crura cerebri, a large mass of gray matter, called locus niger, will be found in the centre of the section. DISSECTION XIV. the internal auditory apparatus. In order to dissect the ear, a recent temporal bone should be obtained; the soft parts, already examined, should be removed. The squamous portion of the bone MIDDLE EAR. 79 is to be got rid of by a vertical cut through the root of the zygoma, and the anterior wall of the osseous portion of the auditory canal is to be cut away with bone for- ceps; this will expose the tympanic membrane. It is extremely difficult, however, to get an idea of the parts contained within the temporal bone; it is only upon a model, or one of the French preparations, that it can be done effectually. The dis- sector may find his work facilitated by softening a recent bone in acid, but with every aid the examination will require a very considerable amount of skill and knowledge. The internal portions of the auditory apparatus are all con- tained within the temporal bone, which also forms a part of the external auditory canal. The tympanic membrane is placed at the bottom of this canal, and separates the external portion of the ear from that constituting the sentient structure. The osseous portion of the auditory canal is about three quarters of an inch in length ; it is furnished with a rough lip, called pro- cessus auditorius, into which the fibro-cartilage of the external ear is inserted ; its lower wall describes a curve, the convexity of which is directed upwards, and the summit of which hides the lower part of the tympanic membrane from view, in examinations with the speculum auris. The membrana tympani is a thin oval membrane, attached by its circumference to a groove in the bone at the inner end of the auditory canal; its surface is convex internally and concave ex- ternally ; it is placed at an angle of 45° with the floor of the canal. One of the little bones of the ear, the malleus, is attached to the upper part of its internal surface, which is also crossed by the chorda tympani nerve. In the foetus this membrane is con- nected with a separate, osseous ring, the tympanic bone, which subsequently unites with the rest of the temporal bone. MIDDLE EAR. The tympanum is behind the tympanic membrane, and is exposed by removing the bone which forms the roof of the cavity, in such a way as to preserve as per- fectly as possible the membrane and the chain of little bones within it. The Tympanum, or Middle Ear, has the form of a round, flat box, placed on edge; the following points are to be noticed within its cavity. Upon the surface, opposite the membrana tympani, a central projection, called the promontory ; above and below this, two apertures opening into the labyrinth; the supe- rior one is called the fenestra ovalis, and the lower fenestra rotun- da ; the fenestra rotunda is closed by a thin membrane, called 80 ANATOMY OF THE HEAD AND NECK. the secondary membrana tympani. The anterior boundary of the tympanic cavity is formed by the membrana tympani and a part of the surrounding bone ; above the membrane may be seen the fissura Glaseri, occupied by the long process of one of the small bones of the ear, the malleus, and by a small muscle, the laxator tympani; crossing the membrana tympani at its upper part, and entering this fissure, is the chorda tympani nerve. This nerve is a long but slender branch of the facial; it arises about a quarter of an inch from the stylo-mastoid foramen, and passes forwards to the tympanum, entering that cavity just below the pyramid; it then crosses the handle of the malleus and membrana tympani to the Glaserian fissure, through which it emerges and unites with the gustatory nerve. It is to be noticed that the circumference of the tympanic cav- ity presents a rough surface, separated superiorly from the cranial cavity, and inferiorly from the jugular fossa, merely by a thin, osseous plate; this is an anatomical fact of importance in connec- tion with fractures of the petrous portion of the temporal bone1 which, if at this point, would lead to serious complications. At the posterior part of the circumference is an orifice leading to the mastoid cells; below this aperture a projection called the pyra- mid, from which a small spiculum of bone extends to the promon- tory ; arching up from the pyramid, above the fenestra ovalis, is a ridge of bone marking the aqueduct of Fallopius. At the ante- rior part of the circumference are the apertures of two canals, the upper one of which contains the tensor 'tympani muscle, and the lower one the Eustachian tube. Between these two canals is a thin, osseous lamina, called processus cochleariformis. The Eustachian tube is the channel through which the tympanic cavity communicates with the fauces ; it is an inch and a half in length, and partly osseous and partly cartilaginous in structure ; its course in the temporal bone is along the angle of union of the squamous and petrous portions, external to the aperture which contains the carotid artery. Its cartilaginous portion has been already described (p. 48). The tympanum contains three small bones. They extend in a line across the cavity, and are named malleus, incus, and stapes. The malleus, so called from its supposed resemblance to a ham- mer, is large at one end (head), and small and tapering at the INTERNAL EAR. 81 other (handle) ; it has two processes, a long and a short; the short process springs from the root of the handle, and the long from a point just above it; the long process extends into the fis- sura Glaseri; the handle is in contact with the membrana tym- pani, and upon the side of its head is an articulating surface which unites it with the next bone, the incus. The incus, or anvil-shaped bone, consists of a body and two processes; the body is concave, to receive the head of the malleus; the two processes, long and short, shoot out from the side of the body, opposite its articulating surface. The long process ends in a rounded extremity called the orbicular process, and sometimes described as a separate bone, under the name of os orbiculare. The orbicular process unites the incus with the third bone, the .stapes. The stapes, resembling in its shape a stirrup, has a base and two sides which unite to form a head. The head is marked by a superficial depression which articulates with the orbicular process of the incus; the base, which is a thin, osseous plate, is fixed over the fenestra ovalis. These bones are maintained in their position by minute liga- ments, which attach them to each other and to the surrounding walls. Three muscles, also, are in connection with the chain of bones. The tensor tympani, the largest of the three muscles, is con- tained in an osseous canal, the orifice of which has already been spoken of as lying above that of the Eustachian tube. It arises from the walls of this canal, and ending in a tendon which turns round the processus cochleariformis as a pulley, is inserted into the inner border of the handle of the malleus, at its base. The stapedius muscle arises from a canal, hollowed in the inte- rior of the pyramid; it ends in a small tendon which is inserted into the neck of the stapes. The laxator tympani arises from the spinous process of the sphenoid bone, and is continued by a long tendon through the fissura Glaseri, to be inserted into the neck of the malleus, above its long process. internal ear. The Internal Ear, or Labyrinth, is composed of an osse- 6 82 ANATOMY OF THE HEAD AND NECK. ous and a membranous portion. The osseous labyrinth consists of the vestibule, the semicircular canals, and the cochlea; the membranous labyrinth, of two sacs, called the utricle and saccule. The vestibule is exposed by enlarging the fenestra ovalis. The Vestibule is an oval-shaped cavity, situated behind the posterior wall of the tympanum; within it are numerous openings; five of these belong to the three semicircular canals, and a larger one, in front of the others, leads to the cochlea. A vertical ridge, called crista, traverses the inner wall; below this is a small circular depression, the fovea hemispherica, perforated by minute orifices which transmit nervous filaments; this depression corresponds to the bottom of the meatus auditorius internus. On the roof of the vestibule is another oval depression called fovea semi-elliptica. Behind the crista, and near the common opening of two of the semicircular canals, is the internal opening of the aquwductus vestibuli, the other orifice of which is on the posterior surface of the petrous portion of the temporal bone ; through it pass a small artery and vein. The semicircular canals may be followed out from their orifices in the vestibule by a file and strong knife; some of the instruments used by dentists are applicable in this and other parts of the dissection of the internal ear. The Semicircular Canals, three in number, are of unequal length, though each forms more than half a circle ; they commu- nicate by both ends with the vestibule ; as two of them, however, blend together, they have but five openings into that cavity. Each canal has a dilated extremity, called its ampulla. From their dif- ferent directions the canals have been named superior, oblique, and horizontal. The superior canal crosses the upper part of the petrous bone transversely, on the anterior surface of which, within the cranium, it makes a marked projection; its ampulla is at the outer end of the canal; its inner end joins with the oblique canal The oblique canal is directed backwards towards the posterior sur- face of the temporal bone ; its inner end is in common with that of the superior canal, and its outer end is furnished with an am- pulla. The horizontal canal is the shortest of the three, and has separate orifices ; it lies in the substance of the bone, nearly on a level with the fenestra ovalis; its ampulla is on the outer side, close above that aperture. The cochlea is anterior to the vestibule. To expose it, the surface of bone form- INTERNAL EAR. 83 ing the 'promontory of the tympanum must be filed or cut away; the surface of the petrous bone above it should also be removed. The Cochlea is conical in form, with its base turned towards the meatus auditorius internus. It resembles a snail-shell in con- struction, consisting of a tube wound spirally round a central part, or axis; the tube makes two turns and a half round the axis, and terminates in a closed extremity, called cupola ; the axis, or mo- diolus, is the bony centre included within the coils of the spiral tube ; its shape is conical, and its size diminishes as it reaches the apex of the cochlea. Winding round the axis is a thin osseous plate, called lamina spiralis, which is projected into the spiral tube, and forms part of a septum, completed by a membrane, which divides that tube into two passages, which, however, commu- nicate at the apex of the cochlea by a foramen, called helicotrema. The lamina spiralis terminates at the apex of the cochlea, in a hook-shaped process, called the hamulus. The two divisions of the spiral tube are called scala, that nearest to the apex being the scala vestibuli, and the other the scala tympani; the scala vestibuli opens by an oval aperture into the anterior part of the vestibule ; the scala tympani is shut off from the vestibule, and terminates at the fenestra rotunda, which is closed by a mem- brane. Communicating with the scala tympani is the aquceduc- tus cochlea, which opens on the under surface of the petrous por- tion of the temporal bone, and transmits a vein from the cochlea to the internal jugular vein. The vestibule, the semicircular canals, and the scalae of the cochlea are lined with a delicate fibro-serous membrane, which secretes a thin fluid called the liquor Cotunnii. The Membranous Labyrinth is composed of sacs, over which the auditory nerve is expanded, and containing a fluid called liquor Scarpa; these sacs are two in number, the utricle and the saccule, and are a perfect counterpart, in form, of the vestibule and semicircular canals. The utricle is situated in the posterior and upper part of the vestibule, opposite the fovea semi- elliptica in the roof. The saccule is smaller than the utricle, and is placed in front of the latter, in the hollow of the fovea hemis- pherica. The membranous tubes for the semicircular canals are prolongations from the utricle. In these sacs are found two 84 ANATOMY OF THE HEAD AND NECK. small calcareous concretions, called otoconites. The membranous labyrinth floats in the liquor Cotunnii. The auditory nerve divides into two branches in the meatus auditorius internus, called the cochlear and the vestibular. The cochlear branch enters by numerous filaments at the base of the modiolus, and these, bending outwards, are distributed upon the lamina spiralis. The vestibular branch divides into three filaments, one of which goes to the utricle and the membranous labyrinth in the ampulla of the superior and horizontal canals; the second to the saccule, and the third to the membrane in the ampulla of the oblique canal. The internal ear is supplied by the internal auditory artery, a branch of the basilar, which enters the internal meatus with the auditory nerve, and divides into two branches, one for the cochlea and one for the vestibule. PART SECOND. ANATOMY OF THE UPPER EXTREMITY, THORAX, AND BACK. DISSECTION I. PECTORAL AND DELTOID REGION. A large block is to be placed under the subject so that the scapulae shall rest upon it, and the arm extended at an obtuse angle with the body; the dissector stands upon its inner side. An incision is made, commencing at the third rib, (a longitudinal incision along the median line of the sternum is supposed to have been already made, when the subject was injected,) and continued in a straight line to about the middle of the arm. The two flaps of skin thus marked out, with the fat and cellular tissue beneath, are then to be successively reflected upwards to the clavicle, and downwards to the limits of the origin of the pectoralis major. This dissection brings the following parts into view:— The Pectoralis major Muscle arises from the sternal half of the clavicle, half of the sternum in its whole length, the carti- lages of all the true ribs, except the last,- and from the aponeuro- sis of the external oblique muscle of the abdomen ; from which a muscular slip is occasionally added, which slip may continue separately from the pectoralis, and have a distinct insertion into the humerus. From this origin the fibres converge to form a flat tendon, inserted into the external ridge of the bicipital groove of the humerus, with this peculiarity, viz: that they are rolled upon themselves, in such a way that the fibres of the upper portion of the muscle are inserted into the lower part of the ridge, and those of the lower portion into the upper part. That part of the muscle arising from the clavicle is separated from that arising from the sternum by a cellular interspace, the size of which, as well as the extent of surface occupied by the sternal origin, varies according to the muscular development or degree of emaciation presented by each individual subject. 86 ANATOMY OF THE UPPER EXTREMITY, ETC. The mammary gland will have been removed with the integument; it is to be examined by removing the fascia and cellular tissue covering its base. The tubuli of the nipple may be demonstrated by the insinuation of a bristle into their ori- fioes. The Mammary Gland rests upon the pectoralis major muscle, and is separated from it only by a layer of fascia. In the male subject the gland is rudimentary ; in the female it varies in size and development. It consists of lobules and lobes, from which issue lactiferous ducts, connected together by fibrous and adipose tissue. The nipple is a conical prominence projecting from the centre of the gland, at which open the tubuli galactophori, about twenty in number, formed by the union of the converging ducts. The nipple is surrounded by an areola or colored ring, the shade of which is influenced by complexion, and upon which numerous papillae will be noticed. The pectoralis major and the deltoid muscle are separated from each other by a groove in which lies the cephalic vein, ascending from the elbow, and an artery, the descending branch of the thoracica acromialis. The deltoid muscle covers the shonlder and cannot be exposed in its totality until the subject be turned upon its face. It is composed of coarse muscular bundles, difficult of dissection from the impossibility of making them tense; this is best effected by bringing the arm down to the side and rotating it firmly inwards. The Deltoid Muscle arises from the external third of the clavicle, from the lower border of the acromion process and from the spine of the scapula, as far as the triangular space in which it terminates, and is inserted into the rough triangular eminence on the outer aspect of the shaft of the humerus. The anterior fibres cover the tendon of the pectoralis major and are in contact with the upper part of the biceps; posteriorly they are bound down by fascia. The dissection of these two muscles completed, the pectoralis major may be di- vided through its middle and the two ends reflected; in so .doing, some offset* of the thoracica acromialis and superior thoracic arteries will be cut across, as well as the short thoracic nerve, given off from the brachial plexus just below the clavicle. On clearing away the fat and cellular tissue, the pectoralis minor muscle comes into view. The Pectoralis minor Muscle arises by three distinct tongues from the third, fourth, and fifth ribs, and is inserted into the anterior border of the coracoid process of the scapula, in AXILLA. 87 common with the short head of the biceps and coraco-brachialis muscles. Connected with the upper border of the pectoralis minor and inserted into the first rib and the coracoid process, and to the clavicle between these points, is a dense fascia called the costo- coracoid membrane. When this is removed it will be found to conceal a small muscle called the subclavius. The Subclavius Muscle arises by a short thick tendon from the cartilage of the first rib, and is inserted into the under surface of the clavicle for more than half its length ; this muscle receives a muscular nerve from the brachial plexus behind the clavicle. axilla. The dissection pursued thus far will have exposed a large space filled with fat, cellular tissue and lymphatic glands, lying behind the pectoralis minor, and through which pass the axillary ar- tery, with its vein and the brachial plexus of nerves ; this space is called the Axilla. The pectoralis minor forms but a small part of its anterior boundary, which is completed by the pectora- lis major; the posterior boundary is formed by the flat tendon of the latissimus dorsi, by the teres major and sub-scapularis muscles ; internally it is limited by the serratus magnus and externally by the biceps and coraco-brachialis muscles. Keeping the arm well extended, patience and a little ingenuity in hooking aside the branches of arteries and filaments of nerves, to make room for the scalpel to reach others, will accomplish the display of the axillary artery and its branches. The brachial plexus of nerves lying upon the outer side of the artery, will, to a certain extent, be prepared in this dissection. Veins which it is impossible to avoid dividing should be tied, so that the blood oozing from them may neither soil nor obscure the dissection. In a locality like this, the dissector will find the scissors a most effective and serviceable instrument. The Axillary Artery is that portion of the artery destined to the upper extremity, intervening between the subclavian and brachial arteries, and extending from the outer border of the first rib to the lower margin of the tendon of the latissimus dorsi and teres major; it passes through the axilla nearer to its anterior than its posterior border. The axillary vein lies in front and at the inside of the artery, and is formed by the union of the basilic vein of the arm and the venae comites of the brachial artery; it receives the cephalic vein near the clavicle, and smaller veins, 88 ANATOMY OF THE UPPER EXTREMITY, ETC. from the muscles, or which accompany the branches of the axillary artery, enter it at various parts of its course. The Brachial Plexus, formed from the anterior branches of the last four cervical, and the first dorsal nerves (p. 45), lies upon the outer side of the axillary artery at its upper part; lower down it surrounds the artery, giving off its branches at various points. Some of these will be described with the dissection of the arm ; those which are given to the thoracic and scapular mus- cles will now be enumerated, though a further reference to them will be made with the dissection of those muscles. These nerves are six in number, viz :— Superior Muscular, Supra-scapular, Short Thoracic, Sub-scapular, Long Thoracic, Inferior Muscular. The superior- muscular supplies the subclavius, rhomboidei, and levator anguli scapulae muscles; it is a branch of the fifth cervical nerve, and is given off from the plexus behind the clavicle. The short thoracic supplies the pectoralis major and minor muscles; there are two of these nerves, and they are given off from the plexus at a point parallel with the clavicle. The long thoracic passes down behind the axillary vessels and plexus, ramifies on the side of the thorax, and is distributed to the fibres of the serratus magnus muscle exclusively; it is a branch of the fourth and fifth cervical nerves. The supra-scapular passing outwards, goes through the supra-scapular notch, and supplies the supra and infra spinatus muscles; it is a branch of the fifth cervical nerve. The sub-scapular are two in number, and are both distributed to the sub- scapularis muscle; one of them comes from the plexus above the clavicle, and the other from the posterior aspect of the plexus within the axilla. The inferior muscular consists of one or more branches, distributed to the teres major and latissimus dorsi muscles; they are given off from the lower part of the plexus. The axillary artery gives off seven branches which vary ex- tremely, however, as to their precise points of origin. In one case in ten, it gives off a larger branch than usual, and this may be either the radial, the ulnar, the interosseous, or a trunk from which arise the sub-scapular, the circumflex, and profunda arte- ries. The regular axillary branches are, Thoracica Acromialis, Thoracica Axillaris, Superior Thoracic, Sub-scapular, Inferior Thoracic, Anterior and Posterior Circumflex. FRONT OF THE ARM. 89 The thoracica acromialis emerges in the space above the border of the pectoralis minor and divides into branches, which are directed inwards to the two pectoral muscles and outwards to the deltoid; from the deltoid set a small twig, called the inferior acromial, passes down beside the cephalic vein in the interspace between the pectoralis major and deltoid muscles. The superior thoracic, (sometimes given off by the preceding artery,) passes along the upper border of the pectoralis minor, distributing branches to the pectoralis major and mammary gland, and inosculates with branches of the internal mammary, emerging between the costal car- tilages near the sternum. The inferior thoracic or external mammary, (sometimes given off from the thoracica acromialis or the sub-scapular,) passes along the lower bor- der of the pectoralis minor and is distributed to the pectoralis major, the mammary gland and the serratus magnus, anastomosing with the supe- rior thoracic and with external branches of the intercostal arteries. The thoracica axillaris is a small artery (arising frequently from one of the other branches) distributed to the nerves and arteries of the axilla. The subscapular is the largest branch of the axillary artery; it passes along the lower border of the sub-scapularis muscle, supplying that mus- cle as well as those of the lower border of the scapula, and gives off a dorsal branch which, passing under its edge, goes to the posterior surface of that bone; this artery and its branches inosculate with the posterior and supra-scapular arteries, branches of the subclavian. To obtain a view of the two remaining branches, the deltoid muscle must be divided and its two ends reflected; in so doing a few small branches of the posterior circumflex will be cut across. The anterior circumflex is a small artery, passing beneath the coraco- brachialis and the short head of the biceps, to wind around in front of the head of the humerus; it sends a small branch through the bicipital groove to the shoulder-joint. The posterior circumflex, much larger than the anterior, passes back- wards beneath the head of the humerus, giving branches to the shoulder- joint, and also, after emerging on the other side of the bone, to the deltoid muscle. These two last-named arteries, together with the profunda, are frequently given off from a common trunk, instead of from the axillary. DISSECTION H. FRONT OF THE ARM. An incision is to be made down the middle of the arm, to a short distance below the bend of the elbow, care being taken not to divide the cutaneous veins or nerves, which near the elbow are quite superficial. The anterior portion of the 90 ANATOMY OF THE UPPER EXTREMITY, ETC. arm is to be cleared from its cellular tissue, the numerous nerves, arteries, and veins being carefully managed whilst the muscles are isolated from each other and the surrounding parts. The insertion of the biceps and brachialis anticus cannot be examined till a subsequent stage of the dissection. In preparing the front of the arm two large veins will have been traced from the elbow upwards; these are the cephalic and basilic. The Cephalic Vein ascends upon the outer side of the biceps muscle to the space between the pectoralis major and deltoid muscles, along which it passes to terminate beneath the clavicle in the axillary vein. The Basilic Vein, superficial at the lower part, pierces the fascia near the middle of the arm, and, accompanying the artery at its inner side, becomes in the axilla, the axillary vein.* The Biceps Muscle constitutes the bulk of the arm in front. It arises by two heads, a short and a long one ; the short head, in common with the coraco-brachialis, arises from the coracoid process of the scapula; the long head arises by a round and slender ten- don from the upper margin of the glenoid cavity of the scapula, passes over the head of the humerus through a special synovial sheath and enters the bicipital groove; emerging from this, it expands into a broader tendon from which the muscular fibres take their origin. These two heads uniting form the belly of the muscle, and this terminating in a flattened tendon, penetrates be- tween the muscles of the fore-arm to be inserted into the tubercle of the radius. An aponeurotic expansion continuous with the fascia of the fore-arm, is given off at the elbow from the outer side of the tendon of insertion, protecting the brachial artery which lies just beneath it. The biceps sometimes has a third head, which consists of a bundle of muscular fibres from the front of the humerus, usually connected with the brachialis anticus, and which unite with the lower part of the belly of the muscle on its inner side. Two or three muscular branches of the brachial artery enter this muscle. The Coraco-brachialis Muscle lies at the inside of the * The first two letters of the word " biceps," that being the muscle with which this vein is in relation, will give the student a mnemonic aid to retain in his mind the relative position of the basilic and cephalic veins. (B. I. basilic, internal.) FRONT OF THE ARM. 91 biceps ; it arises from the coracoid process, between the pectora- lis minor and the short head of the biceps, and is inserted into a rough line on the inner side of the middle of the humerus. The Brachialis anticus Muscle lies beneath the biceps on the lower half of the arm; it arises from the humerus by muscu- lar fibres which embrace the insertion of the deltoid, and is in- serted into the coronoid process of the ulna. Its insertion cannot be fully seen until the fore-arm is dissected. The Brachial Artery extends from the lower border of the tendons of the latissimus dorsi and teres major to the bend of the elbow, where it divides into the radial and ulnar arteries ; it lies along the inner border of the coraco-brachialis and biceps mus- cles and is superficial in nearly its whole extent; the basilic 'vein lies in front of the artery and the ulnar nerve along its inner side ; the median nerve lies first upon its outer side, then crosses it and descends to the elbow on its inner side. The normal condition of this trunk may be varied by what is called the " high division " of the radial, ulnar, or interosseous arteries; that is, instead of originating at the usual point, they arc given off higher up, along the course of the brachial or even of the axillary artery. Sometimes the radial and ulnar, when thus given off, are connected by a transverse branch. Occasion- ally the brachial artery descends with the median nerve to a point near the inner condyle, where it turns around a promi- nence of bone,* and regains its usual position. This is analogous to the ordinary condition of the vessel in some carnivorous ani- mals, in which it passes through a foramen in the humerus, a short distance above the inner condyle. The brachial artery has three branches. Superior and Inferior Profunda. Anastomotica Magna. The superior profunda is given off close below the tendon of the latis- simus dorsi; it passes under, and winds around the humerus, to reappear in the muscular interspace on the outer side of the brachialis anticus where it inosculates with the radial recurrent artery. The profunda sends a branch down the posterior aspect of the humerus to the articula- tion, and this inosculates with the recurrent branch of the posterior inter- osseous artery. The inferior profunda is a small branch given off about the middle of * Called the " supra-condyloid' process " of the humerus. 92 ANATOMY OF THE UPPER EXTREMITY, ETC. the arm; it passes downwards, penetrates behind the inner condyle, and inosculates with the posterior ulnar recurrent. Thi3 artery often arises from the preceding, or is altogether wanting. The anastomotica magna is given off upon the inside of the arm just above the elbow; it runs transversely inwards through the inter-muscular septum to the hollow between the olecranon and the inner condyle, where it inosculates with the inferior profunda and the posterior ulnar recurrent branch. One of its muscular offsets forms an arch across the back of the humerus with a branch of the superior profunda. If the various branches into which the brachial plexus of nerves divides, and which are distributed to the arm and fore-arm, have been carefully followed out, as far as the elbow, in connection with the previous dissection, they will be found to be seven in number, viz:— External Cutaneous, Internal Cutaneous, Lesser internal Cutaneous, Ulnar. The External or Musculocutaneous Nerve arises in common with the external head of the median nerve ; it supplies the coraco-brachialis, which it pierces, and the biceps and bra- chialis anticus, and passes between these two muscles to appear on the outer side of the elbow, where it divides into two branches, both supplying the integuments, the external down to the back of the hand, and the internal as far as the wrist anteriorly. The two following nerves are extremely liable to be removed, with the flap of integument, their small size, and superficial position, leading to their division as they lie unnoticed in the midst of the cellular tissue. The Internal Cutaneous Nerve arises in common with the internal head of the median nerve; it passes down the arm by the side of the basilic vein, giving off cutaneous filaments in its course, and divides into two principal branches, both of which are distributed to the integument of the fore-arm along its inner and anterior aspect. The Lesser internal Cutaneous Nerve, or Nerve of Wrisberg, is the^ smallest nerve of the arm; it is found to the inner side of the internal cutaneous, and is distributed to the in- tegument of the lower part of the arm on its inner side. Just below the axilla, this nerve communicates with the intercosto- Circumflex, Musculo-spiral, Median, BEND OF THE ELBOW. 98 humeral nerve, a branch of the second intercostal nerve, stretching across from the thoracic parietes to the axilla. The Circumflex Nerve is a large trunk which crosses the tendon of the sub-scapularis to pass directly underneath and around the head of the humerus, in* company with the posterior circumflex artery ; it gives branches to the deltoid, the neighbor- ing integument, and to all the muscles of the scapular region. Its sudden turn, and the shortness of its trunk before disappear- ing behind the humerus, sometimes embarrass the dissector in his search for this branch of the brachial plexus. The Musculo-spiral Nerve arises in common with the circumflex; it passes behind the brachial artery, and winds spirally round the humerus, in company with the superior pro- funda, to reach the outer side of the arm, where it lies deep be- tween the brachialis anticus and supinator longus muscles, and divides into two branches,—radial and posterior interosseous. The Median Nerve arises by two heads, which, in the axilla, embrace the brachial artery; it lies at first on the outer side of the vessel, afterwards, on its inner side, and so descends without any branches to the bend of the elbow, where it gives off muscular branches, and the anterior interosseous, and continues down the fore-arm to the hand. The Ulnar Nerve arises in common with the internal head of the median, and internal cutaneous nerves, and descends without branches upon the inner side of the brachial artery, to the hollow between the inner condyle and olecranon, where it gives off muscular and articular branches, and continues down the ulnar side of the fore-arm to the hand. BEND OF THE ELBOW. The veins at the front of the elbow should be studied, with reference to the operation of venesection. A ligature, placed high up around the arm of a living person, affords, in many respects, a better opportunity for studying them, than is found upon the dead-subject. They are generally irregular, and rarely correspond with the description given in the books ; certain re- lationships between them, and the artery and nerves, should, however, be carefully noted. Three superficial veins return the blood from the fore-arm,— 94 ANATOMY OF THE UPPER EXTREMITY, ETC. viz: Radial, Ulnar, and Median, the situations of which are indicated by their names. The median vein divides at the el- bow into two short branches, which unite respectively with the ulnar and radial veins ; the internal branch is called the median basilic, the external, the median cephalic ; the basilic vein being the continuation of the median basilic and ulnar, and the ceph- alic of the median cephalic and radial veins. The disposition of these veins at the elbow, may be compared to the letter M; the middle angle of that letter representing the division of the median vein, the superior lateral angles, the commencement of the cephalic and basilic, and the two limbs at each side, the radial and ulnar veins. The Median Basilic Vein crosses the brachial artery, being separated from it only by the aponeurotic slip given to the fascia of the fore-arm from the tendon of the biceps. Branches of the internal cutaneous nerve pass both in front and behind this vein. The Median Cephalic Vein, smaller than the median basilic, passes outwards along the fold of the elbow, somewhat less superficially; the branches of the external cutaneous nerve pass wholly beneath it. Notwithstanding that in bleeding the operator usually selects the largest vein, it will be seen that the median cephalic presents the more favorable conditions than the median basilic, being away from the artery and above the nerve, whilst the latter, though ordinarily the largest, is not only almost in contact with the artery, but surrounded by nerves. This dissection will at least show the importance of exploring the arm for the pulsations of the artery with reference to its relation to the vein, whichever it may be, that it is proposed to open, if the dangers of traumatic aneurism would be avoided. In the dissection of the elbow, a lymphatic gland will be found with a considerable degree of constancy, just in front of the inner condyle; practically important, as being sometimes enlarged and inflamed from wounds or ulcerations of the hands or finders. STERNAL REGION. 95 DISSECTION III. STERNAL REGION. The further dissection of the upper extremity is now to be relinquished until the thorax and its contents have been examined. It should be carefully wrapped in a bandage and kept constantly moist until its dissection is resumed. The anterior wall of the thorax is to be removed by dividing upon both sides the costal cartilages and intercostal muscles, close to the ribs. If the lungs be free from adhesions, and the pleural cavity has not yet been opened, the student will hear, as he first opens into it, the whistle of the air as it enters the vacuum pre- viously existing, and see the lungs collapse before the atmospheric pressure to which they are then first subjected. If the dissection of the muscles attached to the upper part of the sternum and clavicle is completed, the whole of the sternum may be removed; otherwise a portion must be left by sawing it across^, an inch below its summit. The segment included in the incisions made is to be lifted, first by one and afterwards by both of its lower angles, and the cellular and muscular tissue divided which attaches it to the parts beneath. Its separation at the first rib and from the clavicle is a little difficult, unless properly performed; the knife, as it approaches the first rib, should be directed obliquely outwards till its cartilage is divided, then turning it at right angles to this incision, it is to be carried inwards, gradually describing a curve with the concavity outwards, through the sterno-cla- vicular articulation. Every autopsy which the student attends affords him oppor- tunity of studying nearly all the parts about to be described. Upon the inside of the plastron, as the segment thus re- moved is called, beneath a layer of cellular tissue, will be found the Triangularis Sterni; it arises from the sides of the sternum as high as the third cartilage, the ensiform cartilage, and sternal extremities of the lower three or four costal cartilages, and is inserted by fleshy digitations into the cartilages of the third, fourth, fifth and sixth ribs, and often into that of the second. This muscle varies frequently in its extent and points of attachment. The Internal Mammary,Artery, separated by this section from its origin at the subclavian, descends upon each side of, and about half an inch from the sternum; it gives off the anterior intercostals, which turn outwards in each intercostal space to inos- culate with the aortic intercostals, and give off the branches which perforate the intercostal muscle, close to the sternum, to be distributed to the pectoralis major muscle and the integument of the thorax. A small branch, the comes nervi phrenici, arising as soon as the artery enters the chest, and which descends to the diaphragm with the phrenic nerve, will have been cut off and 96 ANATOMY OF THE UPPER EXTREMITY, ETC. left behind. Some small twigs, called mediastinal and pericardiac, will also be found. At the interval between the sixth and seventh ribs, it gives off a large branch called the musculo-phrenic, which winds along the attachment of the diaphragm to the ribs, and supplies the lower intercostal spaces. The termination of the internal mammary is sometimes called the superior epigastric : it passes downwards between the rectus muscle and its sheath, and inosculates with the epigastric branch of the external iliac. ANTERIOR MEDIASTINUM. The space left between the two pulmonary cavities is called the Mediastinum ; it extends from the summit of the chest to the diaphragm, and from the sternum to the spine. Although there is but one mediastinum, the terms anterior and posterior have been applied to the portions in front of and behind the peri- cardium. The Anterior. Mediastinum contains a quantity of loose cellular tissue, the remains of the thymus gland, the pericardium and heart, arch of the aorta, superior vena cava, with the right and left innominatae veins, bifurcation of the trachea, pulmonary veins and arteries, and phrenic nerves. The Thymus Gland, in the adult subject, consists only of a small quantity of cellulo-adipose tissue; sometimes no trace of it is to be found. In young children it is an organ of considerable size, reaching from just below the thyroid body, half-way to the diaphragm. The Phrenic Nerves, the upper parts of which will have been observed in the dissection of the neck (p. 41), where they arise by filaments from the third, fourth, and fifth cervical nerves, and pass down upon the scalenus anticus muscle to enter the chest, will be here seen passing through the anterior mediastinum on the sides of the pericardium, between it and the pleura. Their course can be traced without dissection, descending to the dia- phragm, upon which they ramify beneath the pleura, the two nerves anastomosing on the under surface of the muscle by filaments, which pass through its fibres. The VENiE Innominate are found in the upper part of the mediastinum. They are formed on each side by the subclavian and internal jugular veins; the union of the two veme innomi- ANTERIOR MEDIASTINUM. 97 natae constitutes the superior vena cava. Sometimes the innomi- nate veins are not united into one, but descend separately to the heart, where both have distinct openings in the right auricle. The Superior Vena Cava is about three inches in length; it passes downwards, piercing the pericardium, to enter the upper part of the right auricle of the heart. Before entering the peri- cardium, it receives the vena azygos major. If the subject being dissected has been injected from the aorta, the pericardium will have been laid open, in order to perform that operation. The Pericardium is the sac containing the heart; it consists of two layers, a fibrous external, and a serous internal. The fibrous layer is attached to the great vessels of the heart above, and to the diaphragm below. The serous layer invests the heart, and is then reflected from it to the fibrous layer, thus forming a shut sac, as serous membranes always do, with the heart in reality lying outside of it. We have only to imagine this sac a globular one to see that the heart, by making a protrusion into its cavity, will not only be covered by a serous surface, but lie in contact with another that is free and external to it. The Heart occupies an oblique position in the chest, its apex pointing to the space between the fifth and sixth ribs, two or three inches from the sternum, and its base towards the right shoulder. It should be observed that the apex is formed by the left ventricle, as, when the organ is opened and emptied of blood, this is not so apparent. The under side of the heart is flattened, and rests upon the diaphragm; its upper surface is rounded. By lifting the heart, and pulling it to either side, the vessels emanating from or entering it will be made apparent, and are to be examined both within the pericar- dium and after their exit from it. On the outside a little dissection will be neces- sary to separate them from one another, and from the bronchial glands and cellular tissue which surround them; part of the pericardium must be cut away. The superior vena cava will be seen entering the pericardium and joining the upper part of the right auricle. The Inferior Vena Cava enters the inferior part of the right auricle as soon as it passes through the diaphragm and pericardium, drawing the root of the heart downwards and giving the organ the oblique position belonging to it. 7 98 ANATOMY OF THE UPPER EXTREMITY, ETC. The Pulmonary Veins are four in number, two for each side; those upon the right are longer than the others and emerge from the right lung in front of the pulmonary artery ; they pass beneath the inferior vena cava and enter the left auricle. The two left pulmonary veins reach the same cavity after a shorter course, passing in front of the descending aorta. These vessels, though carrying arterial blood, are called veins, because like veins they bring the blood to the heart. The Pulmonary Artery ascending from the right ventricle between the two auricles, overlies and partially conceals the aorta; at about two inches from its commencement it divides into the right and left pulmonary arteries ; at the point of division the re- mains of the ductus arteriosus will be found as a fibrous cord extending from this vessel to the aorta. The left pulmonary ar- tery passes under the arch of the aorta and emerging from the pericardium enters the left lung in front and a little above the left primary bronchus. The right artery passes in front of the descending aorta and enters the right lung in front and a little below the right primary bronchus. These vessels, though car- rying venous blood, are called arteries because, like arteries, they carry blood away from the heart. The Arch of the Aorta commences at the anterior part of the left ventricle; emerging between the auricles and behind the pulmonary artery, it ascends, turning gradually to the left, and passing through the pericardium, curves over the left primary bronchus, giving off the large vessels for the head and arms, which will be studied in connection with the neck; it then descends downwards into the posterior mediastinum to become the descend- ing aorta. The portion just described is called the arch, from the curved direction which it takes, and is divided into the ascend- ing, transverse, and descending portions. The ascending is the part within the pericardium; the transverse that from which the great vessels originate, and the descending that portion interven- ing between the last vessel and the lower border of the third dorsal vertebra, where the thoracic aorta begins. The bifurcation of the trachea is the division of that air-tube into the right and left primary bronchus. The right branch is about an inch in length and enters the lung above the right pul- monary artery. The left branch is about two inches in length HEART. 99 and is smaller than the right; it passes obliquely downwards un- der the arch of the aorta and enters the lung below the left pul- monary artery. The bronchus, with the pulmonary artery and vein, constitute what is called the root of the lung. The Bronchial Glands, often numerous and of large size, frequently surround the bifurcation of the trachea. In the adult these are sometimes quite black from carbonaceous deposits, and in scrofulous subjects often contain softened tuberculous and creta- ceous matter. heart. The heart should now be removed for further examination by dividing its vessels at such a point as not to mutilate the auricles. The aorta must be cut across near the heart. The Heart is a muscular organ divided by septa into two similar halves, right and left; each half consisting of two hollow portions, an auricle and ventricle, and each ventricle, conical in shape, being surmounted by its own auricle; the two ventricles form the bulk of the viscus. The auricles are quadrangular in shape with a constricted part in front called the appendix, and have much thinner walls than the ventricles. The appendices auri- culae, project forwards with their indented margins, the left being the longest, and meet each other in front of the great vessels. Externally each cavity is defined by a well-marked line of separ- ation, containing the ramifications of the vessels destined to the proper nourishment of the heart; that between the auricles and ventricles amounts almost to a constriction. A quantity of fat fills up the sulci they would otherwise form. Before opening the heart the vessels on its surface are to be dissected. They are the two coronary arteries and the coronary vein. The Coronary Arteries, two in number, are the first branches of the aorta; they appear on the sides of the pulmo- nary artery and are named right and left. The right coronary appears on the right side of the pulmonary artery and winds round between the right auricle and ventricle to the posterior as- pect of the heart, where it anastomoses with the left coronary artery, which has followed a similar course on the left side. A branch from the right coronary descends posteriorly in the sul- cus between the ventricles. The left coronary passes behind 100 ANATOMY OF THE UPPER EXTREMITY, ETC. the pulmonary artery to emerge on the left side of that vessel and wind round between the left ventricle and auricle to the back of the heart, where it anastomoses with the right coronary artery. The left coronary sends a branch downwards to the apex of the heart in the anterior sulcus between the ventricles. The anterior and posterior cardiac veins accompany these arte- ries and terminate in the Great Cardiac or Coronary Vein ; this occupies the sulcus between the right auricle and ven- tricle posteriorly, and winding round to the front terminates in a dilated ending called the Coronary Sinus ; its termination in the sinus is marked by two valves, and the sinus consists of the por- tion intervening between these two valves and the coronary valve where it opens into the right auricle. The nerves of the heart are furnished by the superficial cardiac plexus, which surrounds the roots of the aorta and pulmonary plexus. The deep cardiac plexus lies between the trachea and the arch of the aorta. These plexuses are derived from the sym- pathetic and pneumogastric nerves, and in them terminate the cervical cardiac branches (p. 39). The right auricle is opened by introducing the point of the scissors into the supe- rior vena cava, and cutting towards, and nearly to, the inferior cava; from the middle of this incision another is made to the tip of the appendix. In the Right Auricle the following parts are to be noticed: The endocardium is the smooth transparent lining membrane, common to all the cavities of the heart, and continuous with the coats of the vessels. When it passes from an auricle to a ventri- cle, or from a ventricle to an artery, it forms duplicatures, or valves, in which fibrous tissue is inclosed. The Eustachian valve is situated between the lower cava and the auriculo-ventricular opening; it is a semi-lunar fold, sometimes rudimentary and sometimes developed into a well-formed valve with a reticulated margin. During foetal life this structure serves to direct the blood from the inferior cava towards the foramen ovale. The coronary valve is occasionally connected with the preced- ing ; this also is a semi-lunar fold stretching across the orifice of the coronary sinus, which enters the auricle just below the inferior cava. The foramina Thebesii are the apertures of minute veins found HEART. 101 in various parts of the cavity, and which, coming from the muscular structure of the heart, pour their contents directly into the auricle. The fossa ovalis is a rounded depression situated on the septum between the auricles, surrounded by a well-defined margin, called annulus ovalis; it is the remains of the foramen ovale of foetal life. Not unfrequently the annulus forms a sort of valve upon one side of the fossa, beneath which a probe may be insinuated and passed into the left auricle, the foramen remaining imperfectly closed; this may be consistent with a perfect condition of the circulation. The musculi pectinati are parallel muscular columns, symmet- rically arranged, and chiefly confined to the parietes of the auricular appendix. The auriculo-ventricular orifice consist of a fibrous ring, with which are connected the folds of membrane constituting the tricuspid valve. The right ventricle is opened by introducing one blade of the scissors through the auriculo-ventricular orifice, and incising its wall along the outer edge, nearly to the apex of the heart; from the ventricle pass the scissors into the pulmonary artery, and make an incision, which, commencing at the termination of the former, shall pass upwards parallel to the ventricular septum, dividing the pulmonary artery. The V-shaped flap thus made, when lifted, will expose the ventricle. The Right Ventricle is remarkable for its fleshy bands and the generally irregular character of the surface of its cavity; near the aperture of the pulmonary artery, however, its walls become comparatively smooth. The columna carnea are the muscular columns, interlacing in all directions, which give the ventricle its characteristic appear- ance. The chorda tendinea are small tendinous bands attached to certain of the columnae carneae, and extending from them to the free edge of the tricuspid valve ; they interlace with each other, and several of them converge to one column for attachment. The tricuspid valve consists of three or more folds of the lining membrane of the heart, strengthened by fibrous tissue, and at- tached by their base to the auriculo-ventricular orifice and by their free edge, which is usually a little thicker than elsewhere, to the chordae tendineae. This valve prevents the regurgitation of the blood from the ventricle to the auricle, the chordae tendinese preventing its flaps from being pressed through into the auricle. The infundibulum is that dilated portion of the ventricle from 102 ANATOMY OF THE UPPER EXTREMITY, ETC. which the pulmonary artery arises ; it has fewer columnae carneae than the rest of the cavity. The lining membrane at the commencement of the pulmonary artery forms three crescentic folds, called sigmoid, or semi-lunar valves. Attached by their convex edge, they are free along the concavity, and look upwards in the course of the vessel. The free margin of these valves is often perforated by small openings, and each one contains in the centre of its concavity a little fibrous nodule, called corpus Arantii; this is sometimes directly at the edge, at other times a little distant from it. Behind each of these valves the pulmonary artery forms dilatations like those similarly placed in the aorta, but not nearly so well marked. The left auricle may be opened by a transverse incision along its ventricular border. The Left Auricle is smaller than the right, but has, how- ever, somewhat thicker walls. It has four openings for the pul- monary veins, two upon each side; occasionally, two of them coalesce. The septum auriculae has, upon this side, no trace of the fossa ovalis, except when an opening remains, and then a small valvular fold may be observed. The musculi pectinati are found only in the appendix. The auriculo-ventricular orifice is smaller than that of the right side. To expose the left ventricle, make a short incision into it with a knife close to the septum; pass the finger through this into the aorta, and upon it, as a director, divide the ventricle and aorta with the scissors, keeping close to the septum, passing between the two appendices auriculae, and holding aside the pulmonary artery, so as not to injure that vessel in making the section. The Left Ventricle is more conical in shape than the right, and its walls are much thicker and more muscular; its surface is irregular from the columnae carneae, but near where the aorta arises the walls are smooth. The mitral valve will have been left undivided if the ventricle is opened as has been directed. It consists of two folds of the Uning membrane, attached to the auriculo-ventricular orifice, and connected to the columnae carneae by chordae tendinea? in a man- ner similar to that described as existing on the right side. The chordae tendineae converge to be inserted in two distinct bundles into the columnae carneae ; they are stronger, but less numerous POSTERIOR MEDIASTINUM. 103 than those of the right ventricle, and the same may be said of the columnae carneae.* The septum venlriculorum seems to form part of the left rather than of the right ventricle, being concave on its left and convex on its right side. The aortic semi-lunar valves are found at the commencement of the aorta, nearly on a level with the mitral valve. They are stronger, though similar in general shape to those of the pulmo- nary artery; the corpora Arantii are more developed, and the dilatations of the vessel behind each segment are much more pro- nounced; they are here called the aortic sinuses, or sinuses of Valsalva. The orifices marking the origin of the anterior and posterior coronary arteries will be observed just behind the semi-lunar valves. Occasionally, these arteries arise from a common trunk, and their number is sometimes increased to three. Their course has been described (p. 99). The student should at some time avail himself of an opportunity to examine the interior of the heart, prepared after the following method. Having washed out the blood and fibrin contained in its cavities, they are to be distended, by filling them from a syringe, with undiluted alcohol, and confining it there by tying all the ves- sels ; then immersing the whole organ in a jar filled with alcohol, in a few days it becomes so stiffened and hardened that it may be opened and the ^nterior exam- ined, by windows cut into the cavities, without its walls collapsing; the valves will be preserved so nearly in their natural condition as to convey a much clearer idea of their character and relations than can be otherwise obtained. DISSECTION IV. POSTERIOR MEDIASTINUM. To examine the posterior mediastinum, the left lung should be lifted from its pleural cavity and turned over to the opposite side, where it should be confined, or held resting in the space that was occupied by the heart. It may be desirable, in order better to get at the parts to be dissected, to remove the anterior halves of the ribs on one side; this can be accomplished by the saw, or bone forceps. *The letters L. M. (so familiar in another connection,) will give the student a mnemonic key to the side to which the mitral valve belongs. (L. M. left, mitral.) 104 ANATOMY OF THE UPPER EXTREMITY, ETC. The Posterior Mediastinum is bounded in front by the posterior surface of the pericardium, behind by the vertebral col- umn, and on each side by the pleura. It contains the thoracic aorta and vena azygos, the oesophagus and thoracic duct, and the pneumogastric and sympathetic nerves. The continuity of the pleura, as it is reflected from the base of the lung to the vertebrae, ribs, and diaphragm, will now be well seen, and perhaps affords the best opportunity of appreciating the manner in which one part of a serous membrane is attached to the parietes of a cavity, and the other to the organ contained in it; the organ being in reality outside of it, and merely pushing inwards the part covering it. The pleura is to be carefully dissected from the subjacent parte, the whole length of the thorax. This will expose the contents of the mediastinum. The Left Pneumogastric Nerve will be found lying upon the anterior surface of the oesophagus; the right pneumogastric nerve is upon its posterior surface. It gives numerous branches to the oesophagus, as it descends upon it to the stomach, where it terminates in gastric branches ; it gives off pulmonary and car- diac branches, and forms a large plexus behind the root of the lung, with which are connected some filaments from the gangli- ated cord of the sympathetic. In the upper part of the thorax it sends off the recurrent laryngeal nerve to pass upwards beside the trachea to the larynx ; upon the left side this nerve curves round the arch of the aorta; on the right it goes round the subclavian artery (p. 41). The Thoracic Aorta commences at the lower border of the third dorsal vertebra; it lies at first upon the left side of the ver- tebral column, and then inclines inwards to the median line ; as it passes through the diaphragm it rests upon the fronts of the ver- tebras. It gives off the following branches, viz :— Bronchial. (Esophageal. Intercostal. The bronchial arteries, two or more in number, and very irregular in their origin, are usually found on the anterior aspect of the aorta, just as the arch ceases to make its curve; they are arteries of considerable size, and pass immediately to the primary bronchi, upon which they ramify in a very tortuous manner, giving small twigs to the oesophagus and peri- POSTERIOR MEDIASTINUM. 105 cardium, and terminating in the parenchyma of the lungs, of which they are the nutrient vessels. The oesophageal arteries vary in number, and are small branches arising from the front of the aorta, afid distributed upon the oesophagus. The intercostal arteries, nine in number, upon each side, are given off from the posterior aspect of the aorta. The right intercostals are the long- est, the position of the aorta obliging them to arch over the bodies of the vertebra. They supply each intercostal space excepting the two upper ones, which are furnished by a branch from the subclavian (p. 44). Each artery is accompanied by a nerve and vein, the former being the anterior branch of the dorsal nerves, and the latter a branch of the vena azygos, and occupies the upper part of the intercostal space, lying in the groove of the lower border of the rib, between the two layers formed by the ex- ternal and internal intercostal muscles; it passes forwards to inosculate with the anterior intercostal branch of the internal mammary, giving off at various parts of its course external branches, which perforate the inter- costal space to go to the muscles and integument of the back and thorax. From one of these branches in the dorsal region a spinal twig goes to the interior of the vertebral canal. The lungs should now be removed, by dividing the trachea just above the bifur- cation. The (Esophagus is a hollow muscular tube, extending from the pharynx to the stomach. The cervical portion is described at p. 48. The thoracic portion enters the chest on the left of the median line, passes beneath the arch of the aorta, to continue on the right side of that trunk to the lower part of the chest, where it again inclines to the left over the aorta and passes through the oesophageal opening of the diaphragm. The oesophagus has a muscular and a mucous coat; the muscu- lar coat is made up of longitudinal and circular fibres, and is con- nected with the mucous by cellular tissue; the mucous coat is of a pale color, and moves freely upon the muscular, the contraction of which throws it into longitudinal folds. The Sympathetic Nerve consists of two portions. The first is the prevertebral portion, made up from the cardiac nerves, descending from the cervical ganglia (p. 39), the branches of which, uniting with filaments from the recurrent laryngeal and pneumogastric nerves, form the cardiac and pulmonary plexuses, distributed over the origin of the great vessels of the heart, the heart itself, the root of the lungs, and the trachea. These can only be satisfactorily studied by special dissections. 106 ANATOMY OF THE UPPER EXTREMITY, ETC. The second or vertebral portion of the sympathetic, consists of a chain of twelve connected ganglia, situated near the heads of the ribs, covered in by the pleura, and continuous with those of the neck and abdomen. The upper ganglion is the largest, and the two lower ones are anterior to the line of the others. Each ganglion furnishes a branch to the intercostal nerves, and from the upper six, small branches are sent to the aorta and medias- tinum. Branches from the sixth, seventh, eighth, and ninth, unite to form the great splanchnic nerve, which passes through the dia- phragm by the side of the crus, to join the semi-lunar ganglion. Branches from the tenth, eleventh, and twelfth ganglia form the lesser splanchnic nerve, which, also piercing the diaphragm goes to the renal and cceliac plexuses. The Intercostal Nerves, twelve upon each side, are the anterior branches of the spinal nerves of the dorsal region. They pass forwards between the two muscular layers of the intercostal space, perforating the external muscle anteriorly, to be distribut- ed to the integument of the front of the thorax. Each nerve receives a short branch from the ganglionic trunk of the sympa- thetic. The first intercostal nerve sends a large branch to join the brachial plexus; the second gives off the intercosto- humeral branch (p. 92), and the twelfth a branch to the first lumbar nerve to assist in forming the lumbar plexus. By removing a portion of the oesophagus, the azygos veins will be brought into view; they are two in number, and are named major and minor. The Azygos Major Vein commencing by branches commu- nicating with the right lumbar and renal veins, and sometimes also with the inferior vena cava, passes through the aortic open- ing of the diaphragm, and ascends upon the bodies of the verte- brae at the right side of the thoracic aorta, receiving the right in- tercostal veins in its course. Opposite the third intercostal space, it arches forwards above the root of the right lung, and enters the superior cava, just before that vessel penetrates the pericardium. The Azygos Minor Vein commences on the left side from the lumbar or renal veins, passes into the thorax with the aorta, or beneath the border of the diaphragm, ascends on the left side of the vertebral column, and at about the seventh or eighth dor- sal vertebra, passes beneath the aorta and thoracic duct, to enter POSTERIOR MEDIASTINUM. 107 the vena azygos major. It collects the lower intercostal veins of the left side. The superior intercostal veins enter a trunk that joins with the left vena innominata, or with the azygos minor. The thoracic duct is difficult to demonstrate or isolate from the surrounding tissues, which it resembles in color; by making a snip with the scissors into the duct, then inserting the blow-pipe, and inflating it, it will become distended, and its course made apparent. The Thoracic Duct commences in an enlargement, to which the lymphatics of the abdomen converge, called the receptaculum chyli; this lies beside the right crus of the diaphragm, between the aorta and vena cava. The duct, about the size of a wheat straw, ascends between the aorta and vena azygos major, crosses the vertebral column at the second dorsal vertebra, and continu- ing upwards along the left side of the oesophagus, enters the left subclavian vein at its junction with the internal jugular. A small duct, called ductus lymphaticus dexter, being the termi- nation of the lymphatics of the head, neck, and portions of the right side of the upper part of the body, enters the right sub- clavian at its junction with the right internal jugular vein (p. 41). The thoracic duct is sometimes double, either in the whole or part of its course. It occasionally empties into the vena azygos major, that being its normal destination, in some mammalia. The duct has been found also on the left side of the aorta. The intercostal spaces are filled by two muscular layers, called external and internal intercostal muscles. The External Intercostal Muscles are eleven in num- ber on each side; they arise from the outer lip of the lower border of the rib, and are inserted into the corresponding part of the rib next below; the fibres run forwards and downwards, and extend from the tubercle of each rib nearly to its cartilage. The Internal Intercostal Muscles, also eleven in num- ber on each side, arise from the inner lip of the lower border of the rib, and are inserted into the upper border of the rib next below; they extend from the sternum to the angles of the ribs, and their fibres are directed backwards and downwards. The internal muscular layer is covered by the pleura, and the inter- costal vessels and nerves ramify between the two muscles. The Infra-costaleb Muscles are bundles of muscular fibres on the inner surface of the ribs, having the same direction as the 108 ANATOMY OF THE UPPER EXTREMITY, ETC. internal intercostals : they stretch across two or three spaces, and vary in size and number. They are most constant on the lower ribs. In three subjects, lying at the same time in the dissecting-room, I have seen the internal mammary artery give off on both sides, from near its origin, a good-sized branch, which might be called an internal thoracic artery; in each instance, it traversed the ribs near their middle, to the fifth intercostal space, where it be- came an intercostal artery. LUNGS. Dissecting-room subjects rarely afford a good opportunity for the examination of the lungs; riddled with tubercular cavities, bound up by old pleuritic adhesions, they are apt to be mutilated in their removal, or rendered puzzling to the student, by their unnatural condition. If uninjured, the lungs should be inflated for their examination. The Lung is conical in shape, and presents a rounded apex that extends above the first rib, and a concave base, or diaphrag- matic surface; the]concavity being greatest in the right lung, owing to the position of the liver; the sharp border of this sur- face penetrating the space between the diaphragm and ribs pos- teriorly, makes the posterior measurement of the lung greater than the anterior. The sides of the lung, with the exception of the mediastinal one, present a smooth convex surface, covered with the pleura, and conforming to the shape of the thoracic cavity. Their mediastinal surface is concave, the position of the heart making the concavity of the left lung the greatest. The anterior border is sharp, and the posterior rounded. Each lung is divided into an upper and lower lobe, by deep fissures, the upper lobe of the right side being subdivided by a more shallow fissure into a third or middle lobe. The lobes are sometimes multiplied, and offer great variety in shape. The lungs vary in color, according to age, or their more or less healthy state; usually, they are of a grayish color, mottled with blackish spots. The sur- face is figured with irregular polygonal outlines, indicating the lo- bules of which they are made up, and these lobules are subdivided by still smaller lines which are the walls of the cells that compose them; the lobules are best seen in infant's lungs, or in those of THE BACK AND POSTERIOR CERVICAL REGION. 109 very young persons. When cut into, the lungs are found to be of a spongy texture, and if in a natural state, upon pressure, the air may be felt escaping in fine bubbles from the air-cells, giving the sensation called crepitation. The lung is made up of the various structures that enter it at its root. The bronchi may be traced by a director and scissors, dividing into principal trunks for each lobe, and then subdividing, until lost by their extreme tenuity; the cartilag- inous rings that were found at their commencement, becom- ing less and less apparent. At the divided root of the lungs, the bronchus is most posterior, and the pulmonary veins anterior, the pulmonary artery being between the two. In the direction from above downwards, the position on the right side is,—bronchus, pulmonary artery, and pulmonary veins; but, on the left side, it is changed to the order —artery, bronchus, and veins. DISSECTION V THE BACK AND POSTERIOR CERVICAL REGION. The dissection of the back, comes next in order, but if the other members of the class are not ready to turn the subject over, the dissection of the arm may be re- sumed, the description of which will be found in Dissection VII. The subject must be turned upon its face, and rest upon blocks, as before; the head should hang over the end of the table, and the arms over its sides; by so doing, the muscles will be put upon the stretch. A longitudinal incision is to be made along the median line, from the occiput to the sacrum, and another from the seventh cervical vertebra to the acromion of the scapula; the flaps, thus formed, are to be raised and reflected. The muscles of the back, always difficult to dissect neatly, are often made more so, by the infiltration of fluids which have gravitated to this part of the body, whilst it remained dependent. The sub-cutaneous cellular tissue is sometimes so much thickened by this infiltration, that it is difficult to tell when the plane of the muscles is reached. If this condition of things exist, care must be taken not to go through the thin aponeurotic tendons by a too hasty incision. The dissection of the back is usually made for the benefit of the class in common, (with the exception of the cervical region, which belongs more properly to the head,) and is generally accomplished by two of the class, the others assisting by reading the description of the parts successively dissected. The student must be prepared to find a great want of conformity between the muscles, as he finds them, 110 ANATOMY OF THE UPPER EXTREMITY, ETC. and the precise description of their origins and insertions as given in his books, for they have little of the distinct arrangement elsewhere to be found. Of many, the fibres are so short, or so incompletely separated, that their isolation is extremely difficult. " The deeper ones," says John Bell, "might fairly be reckoned as one muscle, since they are one in place and in office, but which the anatomist may Beparate into an infinite number, with various and perplexing names, an oppor- tunity which anatomists have been careful not to lose." The trapezius and the latissimus dorsi muscle, form the superfi- cial layer of dorsal muscles, and together cover the whole region of the back. The Trapezius Muscle arises by a thin aponeurotic tendon, easily divided and injured if much care is not taken, from the superior curved line of the occipital bone, the ligamentum nuchas and the spinous processes, and supra-spinous ligament of the last cervical vertebrae, and a variable number (six to twelve) of those of the dorsal region; from this extended origin the fibres con- verge so as to give the muscle a triangular shape a.nd are inserted into the outer third of the clavicle, the acromion process and the spine of the scapula to within an inch of the root of that process; the lower fibres glide over the root of the spine 6f the scapula and sometimes a synovial bursa may be found at that point. The spinal accessory nerve pierces the anterior border of this muscle and is distributed to its fibres. The Ligamentum Nuch.i; is a strong layer of elastic fibrous tissue, extending from the spine of the occiput to that of the seventh cervical vertebra; it is a rudimentary .development of the elastic band which serves to sustain the weight of the head in the Ruminantia. The Latissimus Dorsi Muscle arises from the spinous pro- cesses, and supra-spinous ligament of from four to eight of the dorsal, those of all the lumbar, and two of the sacral vertebr®, from the posterior third of the crest of the ilium, and from three or four of the lower ribs by serrations which indigitate with similar processes of the external oblique muscle of the abdomen; the fibres pass upwards and forwards, to be inserted by a strong flat tendon into the floor of the bicipital groove of the humerus. In their course upwards they overlap the inferior angle of the scap- ula, and beneath them, at this point, a synovial bursa may some- times be found. A distinct fleshy slip is sometimes given off from the lower angle of the scapula, and a muscular band is often seen THE BACK AND POSTERIOR CERVICAL REGION. Ill to stretch across the axilla to terminate in either the pectoralis major or coraco-brachialis. Cutaneous nerves, branches of the posterior divisions of the spinal nerves, will be observed perforating the spinal tendons of both the last-described muscles. A triangular space will sometimes be found intervening between the latissimus dorsi and external oblique, only remarkable as hav- ing been formerly erroneously supposed a point at which intestinal hernia was liable to occur. The latissimus dorsi is covered at its lower part by a layer of the fascia lumborum; this fascia consists of three layers; the superficial, lying upon the latissimus, is attached to the two lower ribs, and the spines of the lumbar vertebras; the middle passes between the erector spinae and quadratus lumborum, and is at- tached to the tips of the lumbar transverse processes ; the inter- nal passes in front of the quadratus lumborum, and is attached to the base of the lumbar transverse processes. These three layers constitute the posterior origin of the transversalis abdom- inis muscle. The trapezius and latissimus are now to be removed by dividing them through the middle of their muscular portions. In reflecting the two ends care must be taken not to push too far the separation between them and the muscles beneath at their spinal attachments, inasmuch as their tendons are united and confounded with those of the next layer. In removing the trapezius, branches of the supra scapular artery will bo divided. The Rhomboideus Minor Muscle is a narrow band arising from the spinous processes, and supra-spinous ligament of the last cervical and first dorsal vertebras, and inserted into the trian- gular space by which the spine of the scapula commences. The Rhomboideus Major Muscle, double the width of the preceding, arises from the spinous processes and supra-spinous ligament of the upper four or five dorsal vertebrae, and is inserted into the posterior border of the scapula, below the spine ; it is separated from the rhomboideus minor by a slight cellular inter- space. These two muscles must be carefully removed, in order to expose those next to be described; in so doing twigs of the posterior scapular artery will be found distrib- uted to them, and that artery must be respected, as it passes along the posterior border of the scapula. The Serratus Posticus Superior is a thin muscular plane, 112 ANATOMY OF THE UPPER EXTREMITY, ETC. arising from the spinous processes of one or two of the last cer- vical and two or three of the upper dorsal vertebrae; it passes downwards and outwards, and is inserted by fleshy serrations into the upper borders of the second, third, and fourth rib9. The Serratus Posticus Inferior, the tendon of which is inseparably connected with the aponeurosis of the latissimus dorsi and the fascia lumborum, arises from the spinous processes of the last two dorsal and first two or three lumbar vertebrae, and pass- ing obliquely upwards, is inserted by fleshy serrations into the last four ribs, each successive process extending further outwards than the one below. A thin aponeurotic lamina, called the vertebral aponeurosis ex- tends between these two last-described muscles, binding down the deeper muscles, and separating them from the more superficial ones. By dividing the serratus posticus superior and the subjacent vertebral aponeu- rosis the splenius muscle will be exposed. The Splenius Muscle, single at its origin, divides into a cer- vical and cranial part, known respectively as splenius capitis and splenius colli. It arises from the spinous processes and ihter- spinous ligaments of the last two cervical and four or five upper dorsal vertebrae, and separating into its two divisions, the splenius capitis is inserted into the space between the two curved lines of the occipital bone and the mastoid process of the temporal, where it is overlapped by part of the sterno-mastoid muscle ; the splenius colli into the posterior tubercles of the transverse processes of three or four of the upper cervical vertebrae. The splenii muscles of the two sides do not meet along the me- dian line, but leave a space between them filled with dense areolar tissue, the removal of which shows the complexus beneath. By dividing the splenius muscle the whole of the levator anguli scapulae will be exposed. The Levator Anguli Scapulae arises by distinct slips from the posterior tubercles of from three to five of the superior cervi- cal vertebrae, between the insertions of the scalenus posticus and splenius, which latter, with the sterno-mastoid muscle, overlaps a portion of it, and is inserted by a fleshy tendon into the superior angle of the scapula. It is sometimes split up into several distinct THE BACK AND POSTERIOR CERVICAL REGION. 113 muscles, the divisions made by its origin continuing down to its insertion. The Omo-hyoid Muscle, connecting the scapula and hyoid bone, consists of two parts, an anterior and posterior. The ante- rior is described at p. 27. The posterior half only is now seen. This portion arises from the upper border of the scapula, behind the supra-scapular notch and from the ligament which converts that notch into a foramen; it forms a thin ribbon-like muscle, directed forwards, and terminates beneath the sterno-mastoid muscle in a tendon which separates its two halves, and which plays through a loop of the deep cervical fascia. The supra-scapular nerve (p. 88) passes through the supra- scapular notch beneath this muscle. The supra-scapular artery (p. 44) also passes beneath this muscle, to the supra-spinous fossa. The posterior scapular artery (p. 44) passes under the levator anguli scapulas, and turns downwards along the base of the sca- pula, beneath the rhomboid muscles, to supply the two surfaces of that bone. In the interstices of the muscles which remain, and in those that will be made in separating them into their different parts, numer- ous small arteries will be seen; in the lumbar region, they are posterior branches from the lumbar arteries ; in the dorsal region, posterior branches from the intercostal arteries; and in the neck, posterior branches from the vertebral arteries, and from the pro- funda cervicis and superficialis cervicis, offsets from the subcla- vian artery. The occipital artery, a branch of the external caro- tid (31), will also be seen emerging from beneath the tendons of the sterno-mastoid, trachelo-mastoid, and splenius muscles, to ram- ify upon the occipital bone; this artery sends off a branch called the princeps cervicis, which passes downwards between the com- plexus and semi-spinalis colli, to inosculate with the profunda cer- vicis. The posterior branches of the sacral, lumbar, dorsal, and cervi- cal nerves, will also be observed; they are mostly small filaments accompanying the arteries, and supplying the muscles and skin. The posterior branches of the first, second, and third cervical nerves are however larger than the others, and form a plexus upon the muscles of the sub-occipital region, called the posterior cervical plexus. The occipitalis major nerve, from the second 8 114 ANATOMY OF THE UPPER EXTREMITY, ETC. cervical, is a branch of considerable size, which passes upwards in company with the occipital artery, and ramifies between the integument, which it supplies, and the posterior belly of the occi- pito-frontalis muscle; it sends numerous branches to the muscles of the back of the neck. Under the title of Erector Spin.e are included a number of muscles of different lengths, extending from the sacrum to the upper part of the neck; small and pointed over the sacrum, in the lumbar region the erector constitutes a single, inseparable mass; in the dorsal region it gradually lessens, and in the neck consists only of slender prolongations. A strong and lustrous, tendinous expansion covers the sacral and lumbar portion; and from this, from the posterior third of the crest of the ilium, the posterior surface of the sacrum, and from the whole length of the transverse processes of the lumbar vertebrae, and the layer of the fascia Hmborum external to these, the erector spinae takes its origin. On a level with the last rib, the muscle begins to sepa- rate into two portions, the external being the sacro-lumbalis, and the internal the longissimus dorsi. The sacro-lumbalis muscle is inserted by separate tendons into the angles of the six lower ribs; here the muscle is reinforced by muscular fasci- culi arising from the upper margins of all the ribs, internally to the pre- ceding insertions, and through them the sacro-lumbalis is continued to the higher ribs, and to the transverse processes of three or four lower cervical vertebras. There is no separation between these accessory fasciculi and the bulk of the sacro-lumbalis; but those derived from the six or eight lower ribs and inserted into the upper ribs, are often described separately, under the name of musculus accessorius ad sacrc-lumbalem; and those from the four or five upper ribs inserted into the transverse processes, as the cervicalis ascendens. The longissimus-dorsi muscle is inserted into the transverse processes of all the dorsal vertebras, and to that portion of from seven to eleven ribs, situated within their angles;—it is continued upwards into the neck by a slender accessory portion, often described as a distinct muscle, under the name of the transversalis colli, and which, arising from the transverse pro- cesses of the upper dorsal and lower cervical vertebrae, is inserted into the transverse processes of about five cervical vertebrae above the preceding, blending with the cervicalis ascendens and trachelo-mastoid muscles. The tracheh-mastoid muscle is the continuation of the longissimus dorsi to the head.. It arises from the tranverse processes of three or four lower 'cervical vertebrae on the inner side of and inseparable from the transver- salis colli, and is inserted into the posterior part of the mastoid process. beneath the splenous and sterno-mastoid muscles. THE BACK AND POSTERIOR CERVICAL REGION. 115 The spinalis-dorsi muscle is often described as a part of the longissimus dorsi, and it can only be artificially separated from it. It arises by sepa- rate tendons from the spinous processes of the first two lumbar and last dorsal vertebras, and is inserted into from four to eight of the spinous pro- cesses of the upper dorsal vertebrae. The muscles of the two sides form a long ellipse. The Complexus Muscle, with the splenius, forms the bulk of the back of the neck. It arises from the transverse processes of four upper dorsal, and from the transverse and articular pro- cesses of four lower cervical vertebrae, and is inserted into the occipital bone between the curved lines. Upon its inner border, a large fasciculus, consisting of two bellies with an intervening tendon, from which it has been named biventer cervicis, separates itself from the principal mass of the complexus. The occipitalis major nerve is transmitted to the surface through the complexus and trapezius, near their cranial attachment. As soon as the nerve is free from the muscles, it receives a cutaneous offset from the third cervical nerve. The occipital artery rests upon the upper end of the complexus, and beneath it the branch of that artery called the princeps cervicis anastomoses with the profunda cervicis. The posterior belly of the occipito-frontalis muscle (p. 3) may be seen at this present dissection. It is a thin, flat plane of mus- cular fibres arising from the outer part of the superior curved line of the occipital bone, and is inserted into the epicranial apo- neurosis, by which it is connected with its anterior, frontal por- tion. The erector spinae, with its accessories and the complexus, are now to be removed by dividing transversely the tendon of the former, close to the sacrum, raising it from the inner side and throwing it outwards. The muscles that remain to be ex- amined, with the exception of the sub-occipital group, are left in a very ragged condition, and obscured by the remains of the numerous tendons and fasciculi divided in the removal of the dissected muscles. It is difficult to make a neat preparation of them. The Semi-spinalis Muscle consists of a thin and narrow stra- tum of short muscular bellies with longer tendons, which stretches from the second cervical to the lower part of the dorsal region; each bundle arising from a tranverse process is inserted into a spinous process, the fibres being directed downwards and out- wards. The upper bundles are larger than the lower ones, and the whole number of them varies in different subjects. Although 116 ANATOMY OF THE UPPER EXTREMITY, ETC. continuous, the upper half of these muscular bundles, those aris- ing from the transverse processes of the four upper dorsal and inserted into the spinous processes of the four upper cervical ver- tebrae, have been named the semi-spinalis colli,—and the lower half, those arising from the transverse processes of the six lower dorsal and inserted into the spinous processes of the four upper dorsal and two lower cervical vertebrae, the semi-spinalis dorsi. The Multifidus Spin.e lies to the inner side and beneath the last-named muscles, and they must be removed in order to see it in its full extent. It reaches from the sacrum to the axis, and consists of a series of muscular slips filling the ver- tebral groove beside the spinous processes. Each fasciculus arises from a transverse process, and is inserted into the spinous process of the first or second vertebra above; the first slip arises from the transverse process of the third cervical vertebra, and is inserted into the spinous process of the axis; the last slip arises from the back of the sacrum, and is inserted into the spine of the fifth lumbar vertebra. The Levatores Costarum are sometimes considered as ac- cessories of the external intercostals; triangular in shape, they arise from the transverse processes of the dorsal vertebrae, and are inserted between the tubercle and the angle of the rib be- low. The inferior levatores sometimes pass over one rib, to be attached to the second below them. There are twelve of these muscles on each side. Between the spinous processes of the cervical and lumbar regions may be found a series of small muscles called Interspinales. In the neck, where the spines are bifid, they are arranged in pairs; they are wanting between the first two cervical vertebrae, and in the dorsal region they are rudimentary; as their name indicates, their origin is from one spinous process, and their insertion that of the next vertebra below it. Similarly disposed to these last are the Inter-transversales Muscles, best marked in the cervical region, where they are arranged in pairs, corresponding to the anterior and posterior tubercles of the transverse processes between which they are arranged; the posterior muscle in the upper inter-transverse space is often wanting. The posterior branches of the spinal nerves emerge between the inter-transversales muscles. SPINAL CORD AND MEMBRANES. 117 A better defined series of muscles remain to be examined; they are those which communicate to the head its peculiar move- ments; they are covered in by an aponeurosis of fibrous tissue, which is to be removed; in so doing the sub-occipital or first cervi- cal nerve is to be respected. The Rectus Capitis posticus major arises from the spine of the axis, and spreading, fan-like, is inserted into and beneath the inferior curved line of the occipital bone. It diverges from its fellow so as to leave a deep interspace between them. The Rectus Capitis posticus minor is placed internal to the preceding; it arises from the posterior border of the atlas, and is inserted into the occipital bone between the inferior curved line and the foramen magnum. The Obliquus Inferior arises from the spinous process of the axis, externally to the rectus major muscle, and is inserted into the transverse process of the atlas. The Obliquus Superior arises from the transverse process of the atlas, passes upwards and forwards, and is inserted just behind the mastoid process, between the curved lines of the occipital bone. The Sub-occipital Nerve, the posterior division of the first cervical nerve, pierces the ligament between the first cervical ver- tebra and the occipital bone, and appears in the interval between the recti and obliqui muscles; it is distributed to these muscles, and sends a branch downwards to communicate with the second cervical nerve. The strikingly symmetrical arrangement of the occipital group of muscles cannot but be noticed. The muscles parting from the spine of the axis form a star with six points; the inferior points being formed by the semi-spinales colli, the lateral by the obliqui inferiores and the superior by the recti capitis majores. SPINAL CORD AND MEMBRANES. The muscles are to be dissected away from the sides of the vertebrae. With the chisel and saw their arches are to be divided on each side close to the articular pro- cesses ; the bone can only be removed piecemeal and wtih difficulty. This done, the membranes of the spinal cord will he exposed. The membranes of the spinal cord are covered externally by some veins and by a loose areolar tissue containing some fat and, especially at the lower part, a little fluid; they are a continua- 118 ANATOMY OF THE UPPER EXTREMITY, ETC. tion of those of the brain, and, like them, consist of dura mater, arachnoid, and pia mater. The Dura Mater envelops the cord loosely, and sends tubu- lar prolongations along the spinal nerves issuing at the interverte- bral foramina; at the lower part of the cord these prolongations become longer and lie for some distance within the spinal canal. The dura mater terminates in an impervious cord which blends with the periosteum covering the back of the coccyx, and lies in the midst of the tubes into which the dura mater divides. The dura mater is to be split longitudinally with the scissors ; this will expose the arachnoid. The Arachnoid is a serous membrane enveloping the spinal cord, and reflected upon the internal surface of the dura mater. That portion attached to the dura mater is closely adherent to it, whilst that in relation to the cord is loose; the interval between the cord and membrane constitutes the sub-arachnoid space, and is filled by a fluid called the cerebrospinal. The arachnoid en- velops each spinal nerve and the collection of nerves terminat- ing the cord. The loose arachnoid is to be removed and the pia mater will then be exposed. The Pia Mater is a thin and stout membrane closely invest- ing the spinal cord ; it forms a sheath for the spinal nerves and inferiorly is prolonged downwards in a slender process called filum terminale, which is blended with the terminal prolongation of the dura mater. On each side of the spinal cord, extending its whole length, and separating the anterior and posterior roots of the spinal nerves, is a white fibrous band, connected internally with the pia mater and having about twenty serrations along its free margin which connect it with the dura mater ; from this peculiarity, and from its supporting the cord, it receives the name of ligamentum denticulatum or membrana dentala. The Spinal Cord is a flattened cylinder giving off thirty-one nerves, arising by two roots and passing out at the intervertebral foramina; they are divided into cervical, dorsal, lumbar, sacral and coccygeal groups, and in each group the nerves are equal to the number of vertebras, except the cervical, which has eight, and the coccygeal, which has but one; as the cervical nerves ex- ceed the number of cervical vertebrae, the lowest nerve of each SPINAL CORD AND MEMBRANES. 119 group is consequently below its corresponding vertebra. Each nerve on emerging from the spinal canal divides into an anterior and posterior primary branch, the former going to the front of the body and the.latter to the back of the trunk. The two roots which blend to form the spinal nerves are called anterior and posterior, or ganglionic and a-ganglionic. The poste- rior roots are the largest, and are each furnished with a ganglion. As the apertures for the transmission of the nerves is not opposite their points of origin, they get an oblique direction, increasing from above downwards; in the lumbar and sacral region their direction is vertical, and the collection of the nerves around the filum terminale is called the cauda equina. It is upon these lower nerves that the ganglion of the posterior root may be best ob- served, as in those nerves given off more nearly opposite their foramina it often lies in the intervertebral canal. The first nerve sometimes wants a posterior root. In the upper part of the canal, the spinal part of the spinal accessory nerve (p. 68) should be sought; it arises by fine fila- ments from the side of the spinal cord as low down as the sixth cervical nerve, and lies between the membrana dentata and the posterior roots of the spinal nerves, with the upper ones of which it is sometimes connected ; it finally enters the skull by the fora- men magnum, to join the accessory part. The spinal cord is supplied by branches from the vertebral arte- ries, which, near their termination in the basilar artery, give off two branches which unite under the name of the anterior spinal artery, to be continued to the bottom of the spinal canal by anas- tomoses from the vertebrals in the neck, and from the intercostal and lumbar arteries. The posterior spinal artery is also derived from the same source, and is continued down the posterior aspect of the spinal canal by anastomoses from the same branches that reinforce the anterior spinal artery. The veins of the spinal cord are very tortuous, and form a plexus on its surface, emptying their contents into the vertebral, intercostal, lumbar, and sacral veins. The spinal cord should be hardened in alcohol for examination, as, soon after death, it becomes softened, and unfit for dissection. The Spinal Cord extends from the pons Varolii to the first or second lumbar vertebra. It has three enlargements, the superior 120 ANATOMY of the UPPER EXTREMITIES, etc. being the medulla oblongata; the middle corresponding to the origin of the nerves for the upper extremity, and the inferior with the origin of those for the lower extremity. It has a fissure along its anterior surface, and another along its posterior surface; the anterior, called the fissura longitudinalis anterior is the widest and the posterior, called the fissura longitudinalis posterior, is the deepest; a lateral fissure also exists along the line of origin of the posterior roots of the spinal nerves, and another has been described as being found along the line of origin of the anterior roots, but its existence is disputed. A transverse section of the cord will show that each of its lat- eral halves is divided by the lateral fissure into two parts, that in front of the fissure being called the anter o-lateral column, and that behind the posterior column ; it will also show that the two halves of the cord are united by a central portion which limits the depth of the longitudinal fissures, and is called the commissure. The lateral halves of the cord are sometimes divided into three columns, called anterior, lateral, and posterior; the anterior being that portion between the anterior roots of the spinal nerves and the anterior longitudinal fissure ; the lateral, that between the two roots; and the posterior, that between the posterior roots of the spinal nerves, and the posterior longitudinal fissure. A transverse section of the cord shows that, like the brain, it is composed of white and gray substance, only here the gray por- tion is surrounded by the white, instead of being external, as in the encephalon. The gray matter is arranged in each half of the cord, in the form of a crescent, the horns of which point towards the roots of the nerves; the convexity looks towards the commis- sure, which also is chiefly made up of gray matter. The posterior horns of the crescents reach to the fissures along the attachment of the posterior 'roots; the anterior horn does not reach to the anterior roots, nor does it form so sharp a point as the posterior. The deep origin of the spinal nerves, like that of the cranial nerves, is uncertain. SCAPULAR REGION. 121 DISSECTION VI. SCAPULAR REGION. The subject should be restored to its position with the face uppermost. All the muscles that attach the upper extremity to the thorax have, with a single excep- tion, been examined, and if they have been divided it will be held only by the clavicle and serratus magnus muscle. The clavicle should be divided in the middle; the bundle of nerves and the artery cut through opposite the second rib and tied in a bunch to the fragment of clavicle remaining. This exposes the serratus magnus muscle. The Serratus Magnus Muscle covers a large portion of the thoracic parietes, and forms the inner wall of the axilla; it arises by nine muscular slips arranged in a curved line, the convexity of which looks forwards, from the anterior surface of eight upper ribs, two slips being attached to the second rib, and the lower of its slips indigitating with the external oblique muscle of the abdomen; it is inserted into the whole length of the posterior border of the scapula. The inferior thoracic and subscapular arteries ramify on the surface of this muscle, and the long thoracic nerve (p. 88) passes down from behind the axillary plexus, to be distributed to it. The division of this muscle will complete the separation of the upper extremity from the thorax. In accomplishing this, it must be remembered that some impor- tant branches of the subclavian artery are distributed to the dorsum of the scap- ula, and these should be so divided as not to interfere with their further examina- tion. The Sub-scapularis Muscle lies upon the inner surface of the scapula, covered in by a fibrous lamina but slightly adherent to it; this removed, it will be found to arise from the inner sur- face of that bone, except at its inferior and superior angles; it is inserted by a broad flat tendon, which forms a part of the cap- sular ligament of the shoulder-joint, into the lesser tuberosity of the humerus. A band of fibres, two or three inches in length, is sometimes found extending from the scapula to the neck of the humerus, just below this muscle. The belly of this muscle is intersected longitudinally by aponeurotic lamina?, attached to the ridges of the scapula. The subscapular nerve, arising from the posterior part of the brachial plexus, will be seen entering this muscle immediately after its origin, penetrating the superior bor- der near the commencement of its tendon ; a small branch enters 122 ANATOMY OF THE UPPER EXTREMITIES, ETC. at the lower border, and a third, accompanying the subscapular artery, is eventually distributed to the latissimus dorsi muscle. The subscapular artery will also be noticed; passing along the lower border, it gives a branch to the deep surface of this muscle, and another to the dorsum of the scapula, and anastomoses with the posterior scapular branch of the subclavian at the inferior angle of the bone. The Teres Major Muscle lies below the sub-scapularis; it arises from the flat surface constituting the inferior angle of the scapula, and leaving a triangular interspace between it and the lower border of the bone, is inserted by a broad tendon, conjoined with that of the latissimus dorsi, into the internal ridge of the bicipital groove of the humerus. A synovial bursa exists between the conjoined tendons. The Supra-spixatus Muscle is situated on the dorsum of the scapula, above the spine of that bone; occupying the whole of the supra-spinous fossa, from the walls of which it arises,it is inserted into the upper facet of the greater tuberosity of the humerus, by a flattened tendon, which forms part of the capsular ligament of the shoulder-joint. Passing through -the supra-scapular notch will be seen the supra-scapular nerve, a branch of the brachial plexus, which passes beneath this muscle to supply it, and then curves round the anterior border of the spine, to be distributed to the infra-spinatus muscle. To trace this nerve, as well as to follow out the divided extremity of the supra- scapular artery, the acromion process should be sawed across at its base, and re- moved; the muscle is thus wholly displayed, and is to be divided near its tendon, and dissected out from the fossa, respecting all nervous and arterial branches that may be exposed. The suprascapular artery is a branch of the subclavian (p. 44), and passes over the ligament of the supra-scapular notch, to penetrate beneath the supra-spinatus muscle, which it sup- plies. A branch winds round the anterior border of the spine of the scapula to inosculate with the dorsal branch of« the sub-scap- ular, and with the branches of the posterior scapular distributed on the dorsum of the bone. The Infra-spinatus Muscle occupies the infra-spinous fossa, and is covered in by a dense fascia, which, as well as the remains of the deltoid muscle, which overlapped its anterior half, BACK OF THE ARM. 123 must be removed. It arises from the walls of the infra-spinous fossa, and from the fascia which covers it externally; it is inserted into the middle facet of the greater tuberosity of the humerus by a tendon which forms part of the capsular ligament of the shoul- der joint. Its tendon is at first concealed by the muscular fibres which overlap it, each half of the muscle being folded over the tendon, from which the fibres diverge in a bipenniform manner. Passing along its outer border is the posterior scapular artery, a branch of the subclavian ; at the inferior angle of the scapula it inosculates with the sub-scapular, and by the offsets which it sends to the infra-spinatus muscle and fossa, it unites with the terminal twigs of the supra-scapular. The Teres Minor Muscle lies between the infra-spinatus and the teres major; it is closely connected with the former, and can oftentimes only be separated from it artificially, so that the dissector is sometimes at a loss to define this muscle, though he may be perfectly aware of its locality. It arises from the inferior border of the scapula, and is inserted into the lower facet of the greater tuberosity of the humerus, its tendon forming part of the capsular ligament of the shoulder-joint. The dorsal branch of the sub-scapular artery curves around this muscle, just outside the scapular head of the triceps muscle, and passes to the infra-spinous fossa, beneath the infra-spinatus muscle, which it supplies, and where it inosculates with the terminal branches of the supra-scapular. back of the arm. The Triceps extensor Cubiti Muscle makes up the whole bulk of the back of the arm ; it has three points of origin, known as its long, middle, and short heads. The long head arises from the inferior border of the scapula, just below the glenoid cavity ; the middle head arises from all the shaft of the humerus below its greater tuberosity, and from the external condyloid rid«re and the intermuscular septum connected with it; the short head arises from the shaft of the humerus below the insertion of the teres major, and from the internal condyloid ridge and its intermuscular septum. These three heads conjoin, to be inserted by a broad aponeurotic tendon into the olecranon process of 124 ANATOMY OF THE UPPER EXTREMITIES, ETC. the ulna; between the tendon and the olecranon is a synovial bursa. The long head of the triceps divides the triangular space left between the teres major and the sub-scapularis muscle into a smaller triangle on the outer side, and into a quadrangular space between it and the humerus on the inner side. Through the small triangular space passes the dorsalis scapulae artery, and through the quadrangular space the posterior circumflex artery, and circumflex nerve. The belly of the triceps is separated from the shaft of the humerus by the musculo-spiral nerve, and the superior profunda artery. The muscle must be divided in the middle, and turned upwards and downward*, to follow out the course of this artery and nerve. DISSECTION VII. FRONT OF THE FORE-ARM. An incision should be made down the fore-arm to the wrist, and there joined by a short transverse one; the skin is to be removed in such a way as to permit the origins of the veins of the elbow to be seen, as well as the terminations of the cuta- neous nerves (p. 92). The muscles of the fore-arm are surrounded by a firm apo- neurosis, which not only invests them collectively, but penetrates between them individually. This aponeurosis is to be divided and removed; towards the condyles it will be found that the muscular fibres originate from it, and where it does, it will necessarily be left adherent to them. The muscles are best isolated from one another by commencing at the tendons, and tracing their separations upwards to the elbow; the sheaths of the muscles and the cellular tissue lying in their inter- spaces must all be removed, and the tendons should be dissected as cleanly as pos- sible ; the beautiful appearance they present when properly dissected fully repayl the labor spent upon them. The tendon of the biceps muscle divides the muscles of the fore- arm into two groups, these groups being collectively attached by a common tendon, which also sends septa between the muscles, one to the inner condyle, the other to the external; they are also divided into a deep and a superficial layer. In separating these muscles, the arteries and nerves will necessarily come into view. It will be seen that the brachial artery dips downward between the mus- cles, and divides into two branches, the radial and ulnar; these pass down the arm between the muscles to the wrist, where they FRONT OF THE FORE-ARM. 125 become comparatively superficial, and then enter the hand. The median nerve lies upon the inner side of the artery, at the hollow of the elbow, and afterwards passes down the middle line of the limb in its course to the hand; the ulnar nerve will be found be- side the ulnar artery in its lower two thirds; the radial nerve also accompanies the radial artery till within three inches of the wrist, where it becomes cutaneous, and divides into two branches, dis- tributed to the thumb and dorsum of the hand. The Pronator Radii Teres is the first muscle next the tendon of the biceps on its inner side; it arises by two heads, one from the inner condyle, and from the common tendon above mentioned, the other deeper, and not to be seen in the present stage of the dissection, from the coronoid process of the ulna; the condyloid attachment sometimes receives additional fibres from the intermuscular septum above the condyle; this peculiarity is usually associated with the existence of a supra-condyloid process. The muscle passes obliquely outwards, to terminate in a flat ten- don that winds round the radius, and is inserted into a rough sur- face on its outer side ; this insertion cannot be seen until the superficial muscles are removed. The median nerve passes be- tween its two heads. The Flexor Carpi Radialis, arising next the pronator, from the inner condyle and the common tendon, becomes tendi- nous near its middle, and is inserted outside the arch of the annu- lar ligament into the base of the metacarpal bones of the index and middle fingers. The insertion cannot be seen till the hand is dissected. The radial artery passes along the outer border of the lower part of its tendon. The Palmaris Longus Muscle lies on the inner side of the flexor carpi radialis; it has a small belly and a long tendon, and is very often wanting; it arises from the internal condyle and common tendon, and continuing down the centre of the fore- arm and over the annular ligament, is inserted into the palmar fascia, with which it is continuous. The Flexor Carpi Ulnaris passes along the ulnar border of the fore-arm, arising from the internal condyle and common tendon, and also from the inner edge of the olecranon, by a strong but thin aponeurosis, underneath which pass the ulnar nerve, and the recurrent branch of the ulnar artery; its tendon receives 126 ANATOMY OF THE UPPER* EXTREMITIES, ETC. short muscular fibres nearly down to the point of its insertion, which is the pisiform bone, and base of the metacarpal bone of the little finger. At its upper part this muscle overlaps the ulnar artery and nerve; below the middle they are upon the inner side of its tendon. The flexor carpi radialis and palmaris longus must be divided Tin their middle and the two ends reflected, as at their upper part they cover up the muscle next to be dissected. The numerous branches of the ulnar artery at the elbow should be carefully preserved. The Flexor sublimis Digitorum forms a large part of the muscular fibres arising from the inner condyle; it also arises from the coronoid process of the ulna and the oblique line of the radius; inferiorly it divides into four tendons which pass beneath the annular ligament to be inserted into the base of the second phalanges of the fingers, as will be seen in the direction of the hand. Beneath the annular ligament the tendons are provided with a synovial membrane. A muscular slip often connects this muscle with the flexor profundus or the flexor longus pollicis. The upper part of the flexor sublimis, where it arises from the radius, is covered by the pronator radii teres, the tendinous inser- tion of which, winding round the radius, as well as its coronoid head, can now be seen. The tendon of the biceps may also be fol- lowed between the muscles to its insertion into the tubercle of the radius. The brachialis anticus will likewise be exposed so that its insertion into the coronoid process of the ulna can be ex- aminee], None of these insertions were seen w,hen the bellies of these muscles were dissected. The Supinator longus Muscle gives the rounded outline characteristic of the outer side of the fore-arm ; it arises from the humerus on its outer side, nearly as high as the insertion of the deltoid, and from the external condyloid ridge; it passes down the radial side of the forearm and is inserted by a flattened ten- don into the external border of the radius, just above the base of its styloid process. The Radial Artery, with its venae comites,lies upon the inner side of the last-named muscle at its upper part, and between it and the pronator radii teres; lower down it lies between the supinator longus and flexor carpi radialis; at its upper part it gives off the radial recurrent branch, which turning backwards beneath the bellv FRONT OF THE FORE-ARM. 127 of the supinator longus sends off numerous muscular twigs and inosculates with the superior profunda from the brachial; in its course to the wrist it gives off many muscular offsets and at the wrist an anterior and posterior carpal branch, which pass trans- versely across in front and behind, to anastomose with similar branches from the ulnar artery. The superficialis vola branch arises from an uncertain point near the wrist and passes on to the ball of the thumb there to lose itself in the muscles or to join with the superficial palmar arch. Having reached the wrist, the radial artery winds round the base of the metacarpal bone of the thumb, beneath its extensor tendons, to enter the palm of the hand be- tween the two heads of the first dorsal interosseous muscle; oc- casionally it curves round the radius higher up than this and sometimes it passes directly over the annular ligament into the palm; its whole course may also be superficial, owing to its high division from the brachial (p 91). The radial artery oftentimes presents, especially in old and fat subjects, a series of flexuosities accompanied by dilatation ; this condition is usually attended by a deposit of calcareous matter in the arterial walls, varying in quantity; the same thing may be noticed in other arteries, and in these cases, ossific or atheromatous deposits will be found to a considerable extent in the upper part of the aorta. The Radial Nerve is the larger of the two branches into which the musculo-spiral nerve divides in front of the external condyle; it accompanies the radial artery upon its outer side beneath the supinator longus muscle; near the wrist it passes under the tendon of the supinator, becomes cutaneous, and divides into two branches, one for the back of the thumb, and the other for the back of the hand. The Median Nerve passes between the two heads of the pronator radii teres, and beneath the flexor sublimis digitorum, where it gives off the anterior interosseous and muscular branches; near the wrist it becomes superficial, appearing along the outer border of the tendons of that muscle; it here gives off a super- ficial palmar branch, which passes over the annular ligament to the muscles and integument of the ball of the thumb, whilst the main part of the nerve continues beneath the ligament to go to the fingers. When the brachial artery passes behind the supra- condyloid process, the median nerve always follows it. The me- 128 ANATOMY OF THE UPPER EXTREMITY, ETC. dian nerve is sometimes accompanied by an artery of considerable size, called the median artery, given off by the anterior inter- osseous or ulnar; it accompanies it to the hand, where it joins one of the palmar arches, or one of the digital branches. The Ulnar Artery, at its origin from the brachial, lies upon the brachialis anticus ; it then dips beneath the flexor sub- limis digitorum, crosses obliquely to the inside of the arm, and emerges at its middle third, becoming more superficial, and lying between the tendons of the flexor sublimis and flexor carpi ulna- ris, to which it gives several muscular twigs ; it crosses the annu- lar ligament under cover of a strong fascia thrown over it from the pisiform bone, and there forms the superficial palmar arch, covered in by the palmar fascia. Just beyond its origin it gives off the anterior ulnar recurrent branch, which passing backwards between the brachialis anticus and pronator muscles, breaks up into muscular branches, and inosculates with the inferior pro- funda and anastomotica magna of the brachial. The posterior ulnar recurrent branch sometimes originates by a common trunk with the preceding, and sometimes is given off a little lower down; it passes beneath the superficial muscles of the inside of the fore-arm, and emerges from beneath the tendon of the flexor carpi ulnaris at the side of the ulnar nerve, and anastomoses with the inferior profunda and anastomotic arteries. The common interosseous artery is given off just below these branches, and its divisions will be hereafter described. The ulnar gives off only muscular branches until it reaches the wrist, where it furnishes an anterior carpal branch to the front, and a posterior carpal branch to the back of the wrist, both of which pass transversely across, to anastomose with similar branches from the radial. In cases of high division, the ulnar artery is usually superficial in the fore- arm. The ulnar artery is accompanied by two venae comites. The Ulnar Nerve, after passing under the attachment of the flexor carpi ulnaris, continues beneath that muscle to about the middle of the fore-arm, where it joins the artery, and descends along its outer side to the wrist; it here gives off a branch which supplies the back of the hand, and then, with the artery, passes over the annular ligament into the palm of the hand, beneath the palmar fascia. BACK OF THE FORE-ARM AND HAND. 129 The flexor sublimis, flexor carpi ulnaris, and supinator longus, are now to be divided across their tendons, and their muscular bellies reflected. The pronator teres may be drawn to one side by hooks. The arteries and nerves may remain undivided. The Flexor profundus Digitorum lies upon the ulna; and arises from the upper two thirds of that bone, and from the interosseous membrane ; it ends in four tendons, which are not, however, separable above the annular ligament, beneath which they pass to perforate the tendons of the flexor sublimis, and be inserted into the base of the last phalanges. The Flexor longus Pollicis lies beneath the supinator longus, and upon the radius ; it arises from the upper two thirds of that bone, from the coronoid process of the ulna, and from the interosseous membrane; its tendon passing beneath the annular ligament, is inserted into the last phalanx of the thumb. The Common Interosseous Artery, after arising from the ulnar, quickly divides into two branches, anterior and posterior. The anterior branch passes down the arm, between or in the deep flexor muscles, in close relation to the interosseous membrane; beneath the pronator quadratus muscle the artery passes through this membrane to anastomose with the posterior carpal branches of the ulnar and radial. The posterior interosseous passes through the interosseous membrane at its upper part, and is distributed to the posterior aspect of the arm. The anterior interosseous nerve, a branch of the median, accom- panies the anterior interosseous artery, and ends in the pronator quadratus muscle. The Pronator quadratus Muscle is a flat quadrilateral muscle, stretched transversely across the lower part of the bones of the fore-arm ; it arises from the anterior surface and border of the ulna, and is inserted into the anterior surface of the radius • the insertion is usually a little narrower than its origin. DISSECTION vTII back of the fore-arm and hand. The skin is to be removed from the back of the arm and hand. The muscles are covered in by a dense fascia continuous with that of the front of the arm • this 9 130 ANATOMY OF THE UPPER EXTREMITY, ETC. may be removed at its lower part, but it is adherent to the bellies of the muscles above; the muscles will be separated by tracing them upwards from their tendons. The back of the arm is more difficult to dissect neatly than the front. Before commencing the dissection of the muscles, the dorsal branch of the radial nerve should be followed out. It becomes cutaneous at the lower third of the radius, and divides into two branches; one of which is distributed to the radial border and ball of the thumb ; the other supplies the remaining side of the thumb, both sides of the next two fingers, and half the ring fin- ger. The dorsal branch of the ulnar nerve, appearing near the styloid process of the ulna, supplies both sides of the little finger, and the contiguous side of the ring finger. The muscles of the back of the arm are divided into two layers; the separation is not quite so defined, nor are the muscles so voluminous as those of the front of the arm. The Extensor Carpi radialis longior lies upon the radial side of the arm, just below the supinator longus, by which it is partly covered; it arises from the external condyloid ridge of the humerus, and its tendon passes through a well-marked groove in the head of the radius, which is covered by the posterior annular ligament, to be inserted into the base of the metacarpal bone of the index finger. The radial nerve lies along the outer border of its tendon. The Extensor Carpi radialis brevior immediately suc- ceeds the preceding muscle, and is partly covered by it; it arises from the outer condyle of the humerus, and the tendon common to the extensor muscles; it forms a tendon closely united with that of the extensor carpi radialis longior, and passes through the same groove in the radius, beneath the annular ligament; after which, it diverges from it, and is inserted into the base of the metacarpal bone of the middle finger. The tendons of both these muscles pass beneath the extensor tendons of the thumb. The Extensor communis Digitorum occupies the central portion of the posterior region of the fore-arm ; it arises from the external condyle by the tendon common to the extensor muscles, and from the intermuscular septa between it and the contiguous muscles; at the lower part of the arm, it divides into three ten- dons, which pass through the annular ligament in a compartment with the extensor indicis; escaping from the ligament, the most BACK OF THE FORE-ARM AND HAND. 131 internal tendon divides into two, and the four tendons pass along the dorsum of the hand, to be inserted into the last two phalanges, forming a flattened sheath for the back of each finger. Oblique tendinous bands connect the tendons with each other on the back of the hand, and upon the fingers they are reinforced by ten- dinous slips from the lumbricales and interossei muscles. The Extensor minimi Digiti is generally a part of the ex- tensor communis ; occasionally it is separable from it. Its origin is the same, and it passes through a separate ring of the annular ligament; its tendon, which is split into two directly afterwards, ends by joining the common expansion on the back of the little finger. The Extensor Carpi Ulnaris arises from the external con- dyle, and the common tendon, and from the upper part of the ulna; its tendon passes through a separate sheath of the annular ligament just over the carpal end of the ulna, to be inserted into the base of the metacarpal bone of the little finger. The Anconeus Muscle is a small triangular muscle placed upon the posterior part of the elbow-joint, which it partly covers, and is sometimes considered as a part of the triceps extensor • it arises from the outer condyle by a distinct tendon posterior to the common tendon of the extensor muscles, and is inserted into the radial side of the olecranon and the adjacent surface of the ulna. The extensor muscles of the arm, which have been described, are now to be divided in the middle, and their two ends reflected; however careful he may have been, the student must expect the deep layer of muscles to present somewhat a ragged appearance. The posterior interosseous artery perforates the interosseous membrane at its upper part, and appears between the supinator brevis and the extensor ossis metacarpi muscles; it descends be- tween the deep and superficial layers of muscles, supplying them with muscular branches, and anastomoses with the posterior car- pal arteries of the radial and ulnar, and with terminal twigs of the anterior interosseous; at its upper part, it gives off a recurrent branch, which passes beneath the anconeus to supply the elbow- joint, and anastomose with a branch of the superior profunda of the brachial. The posterior interosseous nerve is given off in front of the 132 ANATOMY OF THE UPPER EXTREMITY, ETC. outer condyle from the musculo-spiral nerve ; it passes backwards through the fibres of the supinator brevis to descend the arm be- tween the two layers of muscles as far as the middle of the fore- arm, where it sinks beneath the extensor secundi internodii pollicis, and is distributed to the back of the carpus; sometimes it has a gangliform swelling at its termination. The Supinator brevis Muscle is a small muscle at the upper part of the arm, the fibres of which pass obliquely round the upper third of the radius; it arises from the external lateral and the or- bicular ligaments, and from about two inches of the upper part of the ulna, and is inserted into the oblique line on the upper part of the radius, except at its inner part. The Extensor ossis Metacarpi Pollicis lies next below the supinator brevis, and is sometimes united with it; it arises from the posterior surface of the radius, from the ulna, and from the intervening interosseous membrane; it forms a large belly, the tendon of which passing through the outer compartment of the posterior annular ligament, and in a groove of the radius common to it and the extensor primi internodii, is inserted into the base of the metacarpal bone of the thumb. The Extensor primi internodii Pollicis is the smallest muscle of the deep layer, and its tendon is closely connected with that of the preceding muscle ; it arises from the radius and inter- osseous membrane just below the origin of that muscle, and pass- ing through the same space in the annular ligament, is inserted into the base of the first phalanx of the thumb. The Extensor secundi internodii Pollicis lies next below, and is partly covered by the preceding muscle; it arises from the posterior surface of the ulna, and from the interosseous membrane, and passes obliquely to the thumb; its tendon, cross- ing the radial artery and the extensor muscles of the wrist, passes through a special sheath in the annular ligament, and in a groove in the radius, to be inserted into the base of the second phalanx of the thumb. The little triangular interval left between the ten- don of this muscle and the parallel tendons of the two preceding muscles, has been called the " anatomist's snuff-box;" forced abduction of the thumb, will reveal the depression, to which this name is given. The Extensor Indicis is the lowest muscle towards the BACK OF THE FORE-ARM AND HAND. 133 wrist; it arises from the ulna, usually below the middle ; its ten- don passes through the annular ligament with the common exten- sor of the fingers, and uniting with the tendon of that muscle going to the fore-finger, is inserted with it into the second and third phalanx. The Posterior Annular Ligament is formed from the deep fascia of the arm, and if divided over the tendons passing through it, will be found to be made of six separate canals, lined with synovial membrane ; with the exception of that for the ex- tensor minimi digiti, which lies in the interval between the two bones, each of these canals has a corresponding groove in the radius or ulna; between each of the canals, the ligament is firmly attached to the bone beneath. The radial artery will be found passing round the lower end of the radius, beneath the extensor tendons of the thumb, to the space between the thumb and forefinger, where it passes between the two heads of the first dorsal interosseous muscle, and pene- trates into the palm of the hand. Before disappearing, it gives off the dorsal carpal branch, which crosses transversely beneath the extensor tendons, to join a similar branch from the ulnar artery. From the arch thus formed, dorsal interosseous arteries are given off to the third and fourth interosseous spaces; the metacarpal, or first dorsal interosseous, larger than the others, passes up in the space between *he first and second metacarpal bones, and anastomoses, as do the others, with the perforating branch of the deep palmar arch; in the cleft of the finger it ends by joining with the digital branch of the superficial palmar arch. The radial artery also gives off two small dorsal branches to the thumb, and a dorsal branch to the index finger. In addition to its posterior carpal branch, the ulnar artery sends a metacarpal branch along the metacarpal bone of the little finger. The Dorsal Interosseous Muscles are four in number, occupying the spaces between the metacarpal bones, and arising by a double head from the lateral surfaces of the two bones be- tween which they lie. The first is larger than the others, and is called the abductor indicis ; it is inserted into the radial side of the first phalanx and the extensor tendon of the index finger; the radial artery passes between its heads ; the second terminates 134 ANATOMY OF THE UPPER EXTREMITY, ETC. in the first phalanx and extensor tendon of the middle finger on the radial side; the third is also inserted into the first phalanx and extensor tendon of the middle finger, but upon its ulnar side; the fourth is inserted into the first phalanx and extensor tendon of the ring finger on its ulnar side. DISSECTION IX. PALM of the hand. To dissect the hand, the fingers and thumb should be separated widely from each Other and fastened to the table by pins driven through the skin at the tip of each finger. An incision made down the middle of the palm, and another transversely across the roots of the fingers, from which others can be carried down the length of each, will permit the removal of the thick skin and fat covering, and, penetrating between the perforations of a dense fascia, radiating from the annular ligament to the fingers. Upon the ulnar side the student must respect the palmaris brevis muscle, composed of a few bundles of transverse fibres lying in the fat just beneath the integument, and he must be careful not to destroy the transverse ligament, which stretches between the commissures of the fingers. The Palmaris Brevis'Muscle consist of a small though variable number of fibres, arising from the palmar fascia and annular ligament; it passes transversely outwards to be inserted into the integument of the ulnar border of the hand. The ulnar nerve dividing on the annular ligament, sends a superficial branch to the palmaris brevis and two digital nerves which supply both sides of the little finger and the contiguous side of the ring finger. The median nerve also sends an offset across the annular liga- ment which passes down the middle of the palm and unites with one of the superficial branches of the ulnar nerve. The Palmar Fascia, continuous with the anterior border of the annular ligament, spreads out anteriorly, covering in the ten- dons, vessels, and nerves, and opposite each finger divides into slips attached to the sides of the first phalanges; between these, emerge the tendons, nerves, and vessels of the fingers; strong transverse fibres attached to the phalanges on each side, and called the transverse ligament, form a framework over which is PALM OF THE HAND. 135 stretched the skin constituting the commissures of the fingers. The palmar fascia is held down by fibres attached along the metacar- pal bones. The palmar fascia is to be removed with the scissors, preserving the nerves and arteries beneath it; the examination of the muscles of the thumb is then to be pro- ceeded with. The Abductor Pollicis is the most superficial muscle of the thumb; it is flat and narrow, and arises from the annular liga- ment and the os trapezium ; it is inserted into the base of the first phalanx of the thumb; it is oftentimes connected at its origin with a slip from the tendon of the extensor ossis metacarpi pollicis. The Flexor Ossis Metacarpi Pollicis, or Opponens Pollicis Muscle, lies beneath the preceding, its fibres project- ing on both sides; it arises from the annular ligament and os tra- pezium, and is inserted into the whole length of the metacarpal bone of the thumb. The superficialis volae branch of the radial artery crosses these muscles at their origin, and either terminates in their fibres, or continues on to inosculate with the terminal part of the superfi- cial arch of the ulnar artery. It is not always present. The Flexor brevis Pollicis is the largest of the muscles of the thumb ; it has two points of origin, one from the annular ligament and trapezium, the other from the trapezoides and os magnum ; between these two portions passes the tendon of the long flexor of the thumb, which it will be remembered is a brachial muscle (p. 129) ; they then unite into one mass, to be inserted by two heads into the sides of the base of the first phalanx of the thumb, the inner being united with the adductor one, and the outer with the abductor pollicis; a sesamoid bone is connected with each at its insertion. A branch from the median nerve supplies the outer part of the flexor and ends in the abductor and opponens pollicis muscle. The examination of the abductor pollicis muscle is necessarily deferred to a later period of the dissection. The palmaris brevis being removed, the most superficial of the remaining muscles of the little finger is the Abductor Minimi Digiti ; it arises from the pisiform bone and the tendon of the flexor carpi ulnaris, and is inserted into the ulnar side of the base 136 ANATOMY OF THE UPPER EXTREMITY, ETC. of the first phalanx of the little finger. In one instance I have seen this muscle arise from the fascia of the fore-arm with a length of four inches. A branch from the ulnar artery called the communicating, and a deep branch of the ulnar nerve pass between this muscle and the one beneath it. The Flexor brevis Minimi Digiti lies beneath the pre- ceding, of which it appears to be a part; it arises from the unci- form bone and from the annular ligament, and is inserted into the base of the first phalanx of the little finger. This muscle is some- times wanting. The Flexor ossis Metacarpi, Adductor, or Opponens minimi Digiti is partly overlaid by the preceding muscles; it arises from the annular ligament and from the process of the unci- form bone, and is inserted into the whole length of the metacar- pal bone of the little finger. The continuation of the ulnar artery in the palm of the hand is called the superficial palmar arch; it is covered in by the palmar fascia, and lies across the flexor tendons of the fingers and the branches of the median and ulnar nerves; it gives off a deep communicating branch, which passes between the abductor and flexor minimi digiti, to inosculate, as will be seen hereafter, with the deep arch of the radial; it supplies both sides of the three inner fingers, and one side of the index finger, with digital branches; these arise opposite the interosseous spaces by a single trunk, which bifurcates to supply the contiguous sides of two fin- gers, those of the same finger uniting at its extremity ; the branch to the outer side of the little finger arises singly. Near the root of the fingers the digital arteries receive a communicating branch from the deep arch; but the artery to the little finger gets its communicating branch from the deep arch about the middle of the hand. The terminal part of the superficial artery unites with the superficialis volse, and with the branch of the radial artery, which supplies the radial side of the forefinger. The ulnar nerve has already been traced to the supply of the little finger and the contiguous side of the ring finger; it also sends a deep branch which passes between the abductor and flexor minimi digiti in company with the deep communicating branch of the ulnar artery ; this will be followed at a subsequent stage of the dissection. PALM OF THE HAND. 137 The median nerve, after emerging from beneath the annular ligament, divides into two trunks; the external of these, besides giving off a muscular branch to the muscles of the thumb (p. 127), divides into three digital branches, which go to the two sides of the thumb and the radial side of the forefinger; the internal trunk divides into two branches which bifurcate to supply the contiguous sides of the fore and middle, and middle and ring fingers. The digital nerves pass down the sides of the fingers superficial to the arteries and terminate by filaments in the pulp at their extremities. The Anterior Annular Ligament is a firm ligamentous band, beneath which pass the tendons of the flexor muscles; it is attached to the trapezium and scaphoid bone on one side, and to the unciform process and base of the pisiform bone on the other. The canal formed by this ligament is lubricated by a synovial membrane, which surrounds each tendon separately, and is pro- longed both above and below the ligament, sometimes even as far as the fingers, where it communicates with the synovial membrane of the sheaths of some of the tendons; this has been clearly de- monstrated to be nearly constant in the tendons of the thumb and little finger; with the others it is only of occasional occurrence. This continuity in their synovial membranes explains the terrible consequences which sometimes follow phlegmonous inflammations of the fingers. The synovial sac of the wrist and fingers may be demonstrated by insufflation. The annular ligament is now to be divided; the median and ulnar nerves are also to be cut through, and turned over towards the fingers. The tendons of the flexor, sublimis are superficial to those of the deep ; these enter the sheaths of the fingers, and are inserted by two processes into the margins of the middle phalanx about the middle, being split opposite the first phalanx for the passage of the deep flexor tendon. The sheath of the tendons consists of trans- verse tendinous fibres attached to the sides of the first and second phalanx ; in front of the articulations they are either wanting or imperfectly developed; they are lined by a synovial membrane. The tendons of the flexor sublimis are to be divided and reflected towards the fingers. The Lumbricales Muscles are small and delicate muscular 138 ANATOMY OF THE UPPER EXTREMITY, ETC. slips connected with the deep flexor tendons; they are usually four in number, sometimes only three, and occasionally as many as six; they arise from the radial side of the tendon, near the annular ligament, and are partly concealed by the tendons of the flexor sublimis; they are inserted into the tendinous expansion covering the back of the fingers. The tendons of the flexor profundus, the division of which takes place in the palm, enter the sheaths of the tendons of the flexor sublimis, and, through the separations of these, continue onwards to be inserted into the base of the last phalanx. The flexor tendons are attached to the bone and the capsule of the joint posteriorly, by membranous folds containing elastic tissue ; these are called the ligamenta brevia, or vinculo subflava, and are supposed to hold the tendons down when the fingers are bent. The tendon of the flexor longus pollicis passes through the annular ligament externally to those of the profundus; and turns outwards between the heads of the flexor brevis pollicis to be inserted into the last phalanx of the thumb. The deep flexor tendons are to be divided and reflected towards the fingers. The Adductor Pollicis Muscle, obscured by the flexor tendons at an earlier period of the dissection, is now seen arising from the anterior two thirds of the metacarpal bone of the middle finger, on its anterior aspect; its fibres converge to form a small tendon inserted into the inner side of the first phalanx of the thumb. The radial artery enters the hand at the first interosseous space between the two heads of the abductor indicis muscle. It fur- nishes a branch to the thumb, called the princeps pollicis, which divides into two branches, which supply its two sides and inosculate in the pulp ; another branch, either from the radial or from the princeps pollicis, supplies the radial side of the forefinger, and is known as the radialis indicis, and unites at the end of the finger, with the digital branch furnished to the opposite side by the ulnar artery. At the anterior border of the adductor pollicis, the radialis indicis communicates with the superficial palmar arch. The continuation of the radial artery is called the deep palmar arch ; it extends across the interosseous muscles and the meta- -PALM OF THE HAND. 139 carpal bones to the little finger, where it anastomoses with the deep communicating branch of the ulnar artery. The arch sends off recurrent branches, which pass backwards to the carpus and perforating arteries, which penetrate the interosseous muscles to join the interosseous arteries on the back of the hand. Usually there are, also, three palmar interosseous arteries which pass forwards and unite with the digital arteries of the superficial arch at the cleft of the fingers. Although the distribution of the arteries of the hand, which has been described, is the one considered normal, it is to be remem- bered that " it is not possible to know, before a hand is opened, in what manner the arteries are distributed." * Sometimes the radial furnishes the superficial arch, and sometimes there is no arch at all; the arrangement is extremely irregular, and the dis- sector must be prepared to find a very different arrangement from that described. The deep branch of the ulnar nerve accompanies the deep pal- mar arch across the metacarpal bones to the muscles of the thumb, and terminates in branches to the adductor pollicis, the inner head of the short flexor and the abductor indicis. The Palmar Interosseous Muscles are three in number, and are placed upon, rather than between, the metacarpal bones. Theirs* arises from the second metacarpal bone, and is inserted into the ulnar side of the first phalanx and extensor tendon of the forefinger; the second arises from the fourth metacarpal bone, and is inserted into the radial side of the first phalanx and exten- sor tendon of the ring-finger; the third arises from the metacar- pal bone of the little finger, and is inserted into the radial side of the first phalanx and extensor tendon of the little finger. The interosseus and lumbricales muscles being supposed to convey to the hand that peculiar dexterity and delicacy of use which is found only in certain professions or individuals, the dis- secting-room is not the place to find them in their fullest degree of development. * Horner. 140 ANATOMY OF THE UPPER EXTREMITY, ETC. DISSECTION X. ligaments of the sternum, ribs, spine, and upper extremity. To dissect the ligaments, all the fleshy part of muscles surrounding the joints must be removed; the tendinous insertions are to be left, as in many instances they enter largely into the formation of the articulations; the cellular and all other extraneous tissues are to be cleared away, so that nothing shall be left to obscure the pearly aspect which these parts present when properly dissected. Ligamentous preparations are capable of very brilliant display, and though requiring much patience, are extremely interesting to make. The portion of the anterior wall of the thorax, which was re- moved at an early stage of the dissection, furnishes the means of studying the Articulations of the Ribs with the Sternum. The costal cartilages of the true ribs are received into depres- sions on the sides of the sternum, and are fixed in that position by surrounding fibres, the principal of which are arranged in front and behind, and constitute an anterior and posterior chon- drosternal ligament; between the cartilage and the bone is a synovial sac. The seventh rib is attached to the ensiform carti- lage by a special fibrous band, called the costo-xiphoid ligament. The costal cartilages are connected with each other from the sixth to the ninth, at their contiguous surfaces, by ligamentous fibres, and are received into an excavation in the anterior part of the rib, but have no other investment at that point than the perios- teum. A Sternal Articulation is formed between the upper piece of the sternum and the second piece of that bone; each surface being furnished with a concave elliptical cartilage provided with a synovial membrane ; the two bones are held together by an anterior transverse and posterior longitudinal ligament. This articulation is destroyed by the co-ossification of the parts in ad- vanced age. A piece of the spinal column, with three or four ribs attached, furnishes the means of examining the Costo-vertebral and Vertebral Articulations. The ribs are attached to the vertebrae by two groups of liga- ments ; one being from the head of the rib to the bodies of the LIGAMENTS OF THE STERNUM, RIBS, SPINE, ETC. 141 vertebrae, and the other from the tubercle of the rib to the trans- verse process. The head of the rib is received in a hollow on the sides of the bodies of two contiguous vertebrae, except in the first, eleventh, and twelfth ribs, and is thus held in place by the stellate ligament, which passes from it to the vertebrae in a radiated manner, and in those ribs connected with two vertebrae consists of three distinct portions, one for the superior, and one for the inferior vertebra, and a central portion to the inter-vertebral fibro-carti- lage. The inter-articular ligament can only be seen by a vertical and transverse sec- tion, which shall include the bodies of the contiguous vertebrae, and the neck of the rib. The inter-articular ligament is a short, thin band attached on the one side to the ridge that separates the head of the rib into two articulating surfaces, and on the other, to the inter-vertebral fibro-cartilage; it divides the joint into two cavities, each fur- nished with a synovial sac; the first, eleventh, and twelfth ribs have no inter-articular ligament, and consequently, but one syno- vial sac. The costo-transverse ligaments extend between the neck and tubercle of the rib to the transverse processes; the anterior as- cends from the upper border of the neck of the rib to the lower edge of the transverse process of the upper of the two vertebrae, with which it is connected; it is necessarily wanting in the first rib. Between this ligament and the vertebra, emerge the poste- rior branches of the intercostal artery and nerve. The posterior costo-transverse ligament extends from the tubercle of the rib to the tip of the transverse process. The middle costo-transverse ligament can only be seen by a horizontal section, made through the rib and transverse process across the vertebra. The middle, or interosseous transverse ligament, is a very strong band, passing directly between the posterior surface of the neck, and the surface of the transverse process, against which it rests. A synovial sac is found between the tubercle of the rib and the transverse process, except in the lower two ribs, where the tuber- cle and transverse process do not touch. The several vertebrae of the spinal column, are united by liga- 142 ANATOMY OF THE UPPER EXTREMITY, ETC. ments between their bodies and processes ; these correspond throughout the column, except between the first two vertebrae and the head ; these latter are described at p. 59. The anterior common ligament is a broad glistening band that reaches the whole length of the vertebral column ; it rests upon the front of the bodies of the vertebrae; its fibres run longitudi- nally, and are widest opposite the lumbar vertebrae. The posterior common ligament lies on the posterior aspect of the bodies of the vertebrae, reaching from the sacrum to the occipital bone; its fibres run longitudinally, and are in contact with the dura mater; it is widest opposite the cervical vertebras, and as it expands opposite each inter-vertebral disk, it has a scol- loped outline along its borders. The inter-vertebral substance is displayed by separating two ver- tebrae ; it lies between the contiguous surfaces of their bodies, in the form of a circular disk, and consists of a firm, outer, fibrous portion, the layers of which are concentrically arranged, and of a soft and elasjtic central portion, which bulges when two vertebrae are cut apart, or sawn through longitudinally. By separating the inter-vertebral substance from the bone, it will be found that the vertebra has a cartilaginous covering between it and the disk. The processes of the vertebrae have special uniting ligaments. The ligamenta subflava are elastic layers placed between the arches of the vertebrae, stretching from the lower border of one to the upper border of the next; they are longest in the cervi- cal region. The supra-spinous ligament extends along the tips of the spin- ous processes, and in the neck, where it is best developed, it con- stitutes the ligamentum nucha (p. 110). The interspinous ligaments lie between, and extend from the root to the tip of the spinous processes ; they are best marked in the lumbar region. The inter-transverse ligaments extend between the transverse processes, as thin bands in the lumbar, and round bundles in the dorsal vertebrae ; they are wanting in the cervical region. A capsular ligament, not very well marked, surrounds the arti- cular processes, and incloses a synovial membrane. The clavicle is united to the scapula by a joint with the aero- LIGAMENTS OF THE STERNUM, RIBS, SPINE, ETC. 143 mion, and by a ligament between the clavicle and the coracoid process. The Acromioclavicular Articulation is maintained by scattered fibres, which make a kind of capsule for the joint; an inter-articular fibro-cartilage, often indistinct, exists between the two bones, and a synovial membrane lines the interior of the articulations. The coraco-clavicular ligament is a thick fasciculus, reaching from the base of the coracoid process to the under surface of the clavicle; when 6een from the front, its fibres present a quadri- lateral shape, and it is hence called the trapezoid ligament; when seen from behind, they are triangular in shape, and it is then called the conoid ligament. The scapula has two ligaments unconnected with any other bone ; the coraco-acromial, and the transverse. The coraco-acromial ligament is triangular in shape, and ex- tends transversely between the coracoid process and the acro- mion, its apex being attached to the end of the acromion, and its wider base into the whole length of the coracoid process. The transverse ligament converts the notch in the upper border of the scapula into a foramen. The capsular ligament incloses the Shoulder Joint. It is attached above to the neck of the scapula, and below, to the humerus, close to its articular surface ; internally it is lined with a synovial membrane; it is strengthened by the tendons of the muscles of the scapula, and by a broad band, called the coraco- humeral ligament, which extends from the base of the coracoid process to the greater tuberosity of the humerus. The long tendon of the biceps muscle penetrates the capsule between the tuberosities of the humerus, and is attached to the upper part of the glenoid fossa of the scapula; this tendon is surrounded by a prolongation of the capsular synovial membrane. The glenoid ligament consists of a fibrous band, continuous with the tendon of the biceps, and from which it seems to be formed, that surrounds and deepens the glenoid fossa of the scapula. The articulation of the Elbow Joint is kept in place by the following ligaments:— 144 ANATOMY OF THE UPPER EXTREMITY, ETC. The external lateral ligament consists of a roundish fasciculus attached to the external condyle above, and the orbicular liga- ment of the radius below. The internal lateral ligament, triangular in shape, is attached above by its apex to the internal condyle, and below by its base, to the margin of the sigmoid notch of the ulna, from the coronoid process to the olecranon. When the supra-condyloid process is present, a ligament ex- tends from its tip to the internal condyle, thus completing the analogy it is supposed to have with the foramen, through which the brachial artery passes in certain classes of animals. The anterior ligament extends from the front of the humerus to the coronoid process and orbicular ligament; its fibres are very thin and pass in various directions. The posterior ligament is attached superiorly to the humerus above the fossa for the olecranon and inferiorly to the edges of the olecranon process. The radius is held to the ulna by the orbicular ligament, a broad band which surrounds the head of the radius, and is in- serted by its two extremities at either end of the lesser sigmoid notch of the ulna. The oblique ligament is a slender band, sometimes wanting, which extends from the front of the coronoid process to the radius below the tubercle. The tendon of insertion of the biceps muscle may now be examined better than could be done previously; a bursa is found between it and the bone ; near its attachment the tendon changes the direction of its surfaces, the anterior surface becoming exter- nal, and vice versa. The interosseous membrane is a thin fibrous layer, attached to the contiguous margins of the radius and ulna, separating the muscles of the front and back of the fore-arm; its fibres are directed obliquely downwards towards the ulna; superiorly the membrane is wanting. The Wrist Joint is maintained by four ligaments :— The external lateral ligament is a short strong band between the styloid process of the radius and the upper part of the scaphoid bone. The internal lateral ligament is smaller but longer than the LIGAMENTS OF THE STERNUM, RIBS, SPINE, ETC. 145 external; it extends between the styloid process of the ulna and the upper part of the cuneiform bone. The anterior ligament is a membranous layer reaching from the end of the radius to the anterior surface of the first row of carpal bones. The posterior ligament is also a membranous layer, and ex- tends from the lower end of the radius to the posterior aspect of the first row of carpal bones. The radius and ulna are held together at their lower articula- tion by a triangular fibro-cartilage, placed between them; this is attached by its apex to the inner surface of the styloid process of the ulna, and by its base to the edge of the radius ; a few scat- tered fibres loosely surround this joint by way of a capsular liga- ment. The carpal bones are united into two rows by dorsal, palmar, and interosseous bands, and the two rows are similarly united with each other; they are all supplied by one synovial membrane, except the pisiform bone, which has a capsule and synovial mem- brane distinct from the others ; it has also two special ligaments, one to the process of the unciform bone and the other to the base of the fifth metacarpal bone. The Carpo-Metacarpal Articulations are maintained by dorsal and palmar ligaments, excepting in the thumb, which has a capsular ligament connecting it with the trapezium. The metacarpal bones are united at their bases by transverse, dorsal, and palmar ligaments, and by interosseous ligaments, which pass between their contiguous surfaces; these may be demon- strated by tearing the bones apart when the dissection is completed. The Metacarpophalangeal Articulations are main- tained by anterior and lateral ligaments, and by transverse liga- ments, which hold together the heads of the metacarpal bones of the four fingers. The extensor tendon of the finger takes the place of a posterior ligament. The Phalangeal Articulations have three ligaments; the anterior, firm and fibro-cartilaginous, and grooved for the flexor tendons; the lateral ligaments, one on each side, are triangular in form, the apex being attached to the phalanx in front, and the base to the tubercle at the side of the phalanx behind. The ex- tensor tendons supply the place of posterior ligaments. 10 PART THIRD. ANATOMY OF THE ABDOMEN AND LOWER EXTREMITY. DISSECTION I. parietes of the abdomen. A block is to be placed under the lumbar vertebrae, and the abdominal muscles made tense by inflating the peritoneal cavity by a blow-pipe introduced through the umbilicus. A longitudinal incision is to be made from the ensiform cartilage to the pubes, penetrating to the tendons of the muscles; the amount of fat to be divided varies so much that great caution is necessary lest the tendons themselves be wounded; when reached they are known by their white and glistening aspect. From just below the umbilicus a second incision is to be carried upwards and outwards to the most dependent part of the margin of the thorax. The precautions above men- tioned, must also be observed in the inner half of this incision; posteriorly it should penetrate to the muscular fibres. The two angular flaps of integument thus formed are to be reflected upwards and downwards. The dissector must keep close to the tendon, cleaning it carefully and slowly from all the cellular tissue and su- perjacent parts, and when dissecting the muscular portion follow the direction of its fibres, freeing them patiently, one by one, from their sheath, being particularly careful at the point of their junction with the broad flat tendon into which they are inserted, not to divide and dissect up the tendon itself, but to keep it intact in its whole extent. Towards the groin more or less of the fascia should be left, in order to observe its relations to the external abdominal ring. The external oblique muscle cannot be exposed posteriorly without turning the subject over upon its face, or at least upon its side. The abdominal muscles are almost invariably discolored of a greenish hue; this is not usually owing to decomposition, but to the effect of sulphuretted hydrogen in the intestinal canal upon the coloring matter of the blood in the muscular tissue. The Parietes of the Abdomen extend from the median line to the spinal column on each side, and from the ribs above to the pelvis below; they are made up of three pairs of flat rnus- PARIETES OF THE ABDOMEN. 147 cles, disposed in layers, and the direction of whose fibres is differ- ent ; in front they terminate in extensive aponeuroses, also dis- posed in layers, and between them on each side of the median line extends a single long muscle. The abdomen is covered by a fascia and a very variable amount of fat. The superficial fascia is continuous with that of the thorax and lower extremity. No special dissection of it is necessary. It is only important in the inguinal region, where it divides into two layers, and, as will hereafter be seen, bears certain relations to the surgical affection called hernia; these two layers art; sep- arated by the superficial epigastric artery and vein, the former being a small branch from the femoral, arising below Poupart's ligament, and passing upwards towards the umbilicus. It will be seen that certain fibres of the superficial fascia pass from the pubes to the penis, forming a rounded cord called ligamentum suspenso- rium penis. In the groin it attaches itself to Poupart's ligament, and through that becomes blended with the fascia of the thigh; it covers the spermatic cord, and, accompanying it to the scrotum, there unites with the fascia of the perineum. Between its two layers, and above Poupart's ligament, three or four lymphatic glands will be found; these receive the lymphatics from the abdomen and genital organs, and their efferent ducts pass in at the saphenous opening of the thigh. The Obliquus Externus Muscle is the most superficial of the abdominal muscles ; it is aponeurotic in front and fleshy upon the side; it arises from the external surface of eight or nine lower ribs by processes called digitations, which are received between similar processes belonging to the serratus magnus and latis- simus dorsi. It is inserted into the outer edge of the ante- rior half of the crest of the ilium and its anterior superior spi- nous process, into the spine, pectineal line and front of the os pubis, and into the whole length of the linea alba. The portion inserted into the crest of the ilium is fleshy; the remainder consists of a spreading aponeurosis, connected above with the pectoralis major muscle, and along the median line uniting with the muscle of the other side; this interlacement of their fibres forms what is called the linea alba, in the centre of which is the umbilicus, being the point at which the umbilical artery and vein composing the umbilical cord, were divided at the time of birth, and have 148 ANATOMY OF THE ABDOMEN, ETC. become obliterated. Between the anterior superior spinous process of the ilium and the spine of the pubis, its fibres become rolled into a sort of cord, known as Poupart's ligament, and continuous by its lower border with the fascia lata of the thigh. When properly dis- sected, small foramina will be noticed in the aponeurosis, giving exit to the cutaneous nerves and vessels ; the nerves are btanches of the intercostals, and of the lumbar plexus, and the arteries are chiefly from the internal mammary, lumbar, and circumflexa ilii. The outline of the rectus muscle can be plainly seen through the tendon of the external oblique; the curved line which indicates its external border and extends from the os pubis to the chest is called the linea arcuata. At the pubes the fibres of the apo- neurosis split, and leave a space which affords passage to the sper- matic cord in the male and the round ligament in the female; this space is very variable in size, and is usually larger in the male than the female subject; although there is nothing annular in its conformation to give it such a name, it is called the external abdominal ring. The fibres forming its superior border or pillar interlace with those of the opposite side in front of the symphysis; its inferior border or pillar is formed from the internal portion of Poupart's ligament. Just above the spermatic cord this separa- tion in the aponeurosis is traversed by a series of transverse fibres, variable both in size and number ; they extend for a con- siderable distance on either side of the pillars, and constitute what are called the inter-columnar fibres. Between the pillars, covering in the cord and prolonged upon it, is a thin and delicate expansion called the spermatic fascia; if this is divided trans- versely upon the cord, the handle of a scalpel may be passed un- der it and pushed upwards beneath the tendon ; this will demon- strate its existence as a layer distinct from the elements of the cord. The external oblique is to be removed by dividing it transversely across its fleshy part; the change in the direction of the fibres will show when the internal oblique is reached. In accomplishing the separation of these two muscles, the fescia of the internal muscle should be removed with the external. In order to reserve the in- guinal region, the tendon should be divided transversely from the anterior superior spinous process to the linea alba, and down the linea alba to near the pubis, so far as the close union with the muscle beneath will permit, the portion below being left for further examination. The obliquus internus is thus exposed, except at its lower part, which, by a little manipulation, may also be seen on turning downward that portion of the external oblique which has been left attached. PARIETES OF THE ABDOMEN. 149 The Obliquus Internus Muscle arises from the outer half of Poupart's ligament, from the anterior two thirds of the crest of the ilium, and from that portion of the lumbar fascia which is attached to the spinous processes of the lumbar vertebrae. The fibres of the lower part of this muscle are thin, and separated from each other ; they curve over the spermatic cord, or round ligament, and uniting with the tendon of the muscle beneath, under the name of the conjoined tendon of the internal oblique and transversalis, are inserted into the crest of the pubis and the pec- tineal line behind the tendon of the external oblique. The re- mainder of the fibres pass upwards and inwards, and terminate in an aponeurosis at the outer border of the rectus muscle. The upper half of this aponeurosis splits into two laminae, which encase the upper half of that muscle, and meet on the median line ; the whole of the aponeurosis passes in front of the lower half of the muscle, blending with the tendon of the external oblique. Along the linea alba, the tendons of the two sides unite inseparably. Superiorly the muscle is inserted into the lower border of the cartilages of the last four ribs. In arching over the spermatic cord, certain of the muscular fibres are prolonged, and carried downwards in long loops, by the testicles at the period of their descent; these fibres may be seen as a muscular layer upon the cord, and are called the oremaster muscle; they vary very much in distinctness, and do not exist in the female subject. They are sometimes described as coming from the transversalis muscle, as well as the internal oblique, the two muscles being intimately blended at this point. The separation of this muscle from the next, is with difficulty accomplished in a manner that leaves the transversalis neatly and fairly exposed The fibres of the internal oblique should be divided transversely to their direction; the .different direction of its fibres and the ramifications of vessels in the space between the muscles, will tell when the transversalis is reached; the internal oblique is to be dissected away from it, and divided from its own tendon along the outer edge of the rectus muscle. The lower fibres, which assume a similar direction to those of the transversalis, and to a certain extent become confounded with them, may be left behind, with reference to a more special examination of the inguinal region in relation to hernia. The Transversalis Muscle arises from the outer half of Poupart's ligament, from the anterior three fourths of the inner lip of the crest of the ilium, from the lumbar fascia, i. e., from the spinous and the tips and bases of the transverse processes of 150 ANATOMY OF THE ABDOMEN, ETC. the lumbar vertebrae, and from the under surface of the last six or seven ribs, where it indigitates with the diaphragm. Its "fibres pass transversely forwards, and terminate in an aponeu- rosis, the upper two thirds of which goes behind, and the lower third in front of the rectus muscle, and is inserted into the linea alba. The lower fibres of the muscle cover over the sper- matic cord, or round ligament, and are inserted into the pectineal line, in connection with the lower fibres of the internal oblique, under the name of the conjoined tendon ; these lower fibres are small, and separated from each other; indeed, the portion arising from Poupart's ligament, is sometimes deficient, and at others confounded with, and inseparable from, the internal oblique; in either case, the transversalis fascia and peritoneum, may be seen through the fibres: the internal oblique usually descends nearest to Poupart, whilst the transversalis makes up the greater part of the conjoined tendon. The circumflexa ilii artery, a branch of the external iliac, and the musculocutaneous nerve from the lumbar plexus, ramify upon and in this muscle above the crest of the ilium. The rectus muscle is exposed by dividing the aponeurosis which covers it in front from the sternum to the pubis, at about an inch from the median line; at two or three points this sheath will be found adherent to certain tendinous intersections which traverse the muscle; the aponeurosis should be carefully dissected from them. The Rectus Muscle, broad above and narrow below, arises by a thick tendon from the crest of the os pubis; becoming thin- ner as it grows broader, it is inserted into the cartilages of the fifth, sixth, and seventh ribs; it is separated from its fellow by an interval, formed by the aggregation of the fibres of the tendons of the abdominal muscles of the two sides which constitutes the linea alba. Two or three tendinous intersections, sometimes complete, at others only partial, cross the rectus in irregular directions; they are called linea transversa, and serve to keep the muscle flat during its contractions, since without them, its broad insertion and narrow origin, would give it a tendency to roll into a cone, longitudinally. The rectus muscle is occasionally inserted as high as the fourth, or even third rib. Sometimes there may be found an abnormal muscle upon the sternum, which appears, physiologi- cally at least, to be a continuation of this muscle; it is called the rectus sternalis, and is described as being occasionally connected PARIETES OF THE ABDOMEN. 151 with the sterno-mastoid, instances being reported where the sterno-mastoid and rectus were one continuous muscle. This occasional slip, and the high insertion of the rectus, is looked upon as corresponding with the long rectus of the lower orders of animals. The rectus muscle should be divided at the umbilicus; the two ends will be easily dissected up from their posterior cellular attachments, and it will then be seen how it is encased by the aponeurosis of the abdominal muscles. In front of the upper half of the rectus muscle, is the tendon of the external oblique, and the anterior layer of that of the in- ternal oblique ; behind the upper half is the posterior layer of the tendon of the internal oblique, and the whole of that of the trans- versalis. Below the umbilicus all the tendons pass in front, whilst behiud, the rectus is separated from the viscera only by the trans- versalis fascia and the peritoneum. The lower edge of the tendons forming the posterior sheath of the upper half of the rectus muscle assumes a crescentic shape, and is called the semi-lunar fold of Douglass ; the space below this fold, between the peritoneum and the muscle, Retzius has described as a "pre-peritoneal cavity," having proper walls formed by the transversalis fascia, and des- tined to accommodate the bladder in its changes of volume, and enabling the recti muscles to act more directly upon it in empty- ing it of its contents. Below the umbilicus, the linea alba be- comes more tendinous than above that point, and the peritoneum is manifestly less closely connected with the abdominal walls. The epigastric artery, a branch of the external iliac, will be seen penetrating the lower half of the rectus, and lying loose between it and its sheath for a portion of its course; if well injected, it may also be traced in the fibres of the muscle to an anastomosis with the terminal branches of the internal mammary artery. It was by the aid of these anastomoses, that some of the old anato- mists endeavored to explain the intimate relationship between the genital organs and the mammary gland. The Pyramidalis Muscle, small and triangular in shape, lies upon and inclosed within the sheath of the rectus, and is, as it were, accessory to that muscle, which becomes enlarged at its lower part when it is absent; it arises from the front of the os pubis, and, tapering as it goes upwards, is inserted into the linea alba from two to four inches above the symphysis. One or both of these muscles is very commonly wanting. 152 ANATOMY OF THE ABDOMEN, ETC. ANATOMY OF INGUINAL HERNIA. It is always desirable, if possible, to make a special dissection of the inguinal region; but if the student has left the lower part of the abdominal muscles as di- rected, they may be very satisfactorily examined after the general dissection is ac- complished. The dissection can be advantageously performed only upon th,e male subject. Under the influence of violent exertions, and sometimes pas- sively, a portion of the contents of the abdomen may be protruded at such parts of its walls, as, from their conformation, are weaker or less protected than others. This protrusion is called hernia, or rupture. The inguinal region is a point at which it frequently occurs. To understand why this region is liable to this accident, and what means are to be resorted to for its relief, it is necessary to examine it specially in this relation. The Inguinal Region is included between Poupart's liga- ment, the linea alba, and an imaginary line from the latter to the anterior superior spinous process of the ilium; most of its parts have already been separately described. The perforation of the external oblique by the spermatic cord, the thinness, or partial deficiency of the fibres of the internal oblique and transversalis muscles, make it apparent that less resistance would be offered here than elsewhere to the superincumbent weight of the abdom- inal viscera, and that their impulsion against it, during efforts that contracted the diaphragm and abdominal muscles, would render a rupture a very conceivable occurrence. The superficial fascia, but for its relation to the anatomy of hernia, would be considered merely as the sheath of the external oblique, in which" a certain amount of fat was deposited. It is usually spoken of as consisting of two layers, separated by the superficial epigastric artery and vein. Unless a special dissection of it has been made, it will probably be found that one of these layers has been removed with the skin. Directly beneath this, is the tendon of the external oblique, between the fibres of which emerges the spermatic cord. This point of emergence is called the external abdominal ring, and consists merely of a separation of the tendon, the upper border of which is called the superior pillar, and the lower, the inferior pillar of the ring. The further separation of these pillars is prevented by transverse fibres, called inter-columnar. The spermatic cord consists of the excretory duct of the testicle, called the vas deferens, the spermatic artery and ANATOMY OF INGUINAL HERNIA. 153 vein, a nerve, some lymphatics, and cellular tissue. These con- stitute a bundle of considerable size, the whole of which lies behind a thin fascia, extending across the pillars of the external ring, and continued down upon the cord, called the spermatic fascia. Upon reflecting the lower part of the external oblique, towards the groin, the spermatic cord will be observed lying for a short distance behind it; the internal oblique and transversalis curve over it, and Poupart's ligament is directly beneath it. The cre- master muscle, being fibres of the internal oblique and transver- salis, lies upon the cord itself, and its connection with those muscles may possibly be traced; The space traversed by the cord behind the external oblique, is called the inguinal canal. If the internal oblique and transversalis are separated, upon turning down the lower part of the former muscle, it will be seen that the transversalis leaves a space between itself and Poupart's ligament; in this space will be seen the transversalis fascia, and upon reflecting the transversalis muscle, it will be seen lying be- hind it, upon the peritoneum. This, like the superficial fascia, were it not for its relations to hernia, would be considered merely as the sheath of the transversalis muscle ; it is of very variable thickness, sometimes amounting to nothing but a little cellular tissue; it is attached to Poupart's ligament below, and internally to the conjoined tendon and sheath of the rectus muscle. By pulling the spermatic cord, it will be seen that this fascia is reflected from the peritoneum on to the surface of the cord, and the cone that is thus formed and made apparent by this traction, is called the infundibuliform fascia. The orifice form- ing the base of this cone, and across which the peritoneum is stretched, is the internal abdominal ring. By incising the fas- cia on the peritoneum, the handle of a scalpel may be inserted, and pushed down the cord between it and that portion of the transversalis fascia, just described as the infundibuliform, show- ing that at this point, the peritoneum might be protruded before a knuckle of intestine, and if forced onwards, must pass down in the direction taken by the knife-handle, between the fascia and the cord. The epigastric artery lies between this fascia and the peritoneum; it passes under the cord close to the inguinal ring; the vas deferens hooks over it as it turns downwards into the pelvis. A large triangular flap of the peritoneum being incised and 154 ANATOMY OF THE ABDOMEN, ETC. turned towards the groin, it will be noticed that upon the median line, there is a cord passing from the bladder to the linea alba ; this is the remains of the allantois of fcetal life; another cord, being the remains of the obUterated hypogastric artery of fcetal life, passes obliquely from the umbilicus downwards towards the pelvis, in a line nearly corresponding to that of the epigastric artery: this cord, by its shortness, causes the peritoneum to make a pouch on each side,—these are called the inguinal fossa ; one of them is behind the external ring, and the other behind the internal ring, and it will be seen that each must direct that portion of intes- tine which accidentally lies within it, towards the ring that lies in front of it, and as the abdominal wall corresponding to the external ring is weaker than elsewhere, owing to the loss, at that point, of one of the layers constituting its thickness, and at the internal ring, owing to the conformation already described, it follows that a hernia is liable to occur at either situation; it is called a direct hernia, if it protrudes from directly opposite the external ring, and an oblique hernia, if it enters the internal ring, and follows the direction of the spermatic cord. By pulling upon the spermatic cord, the peritoneum will exhib- it, at the part affected by the traction, a puckered appearance; this is the point at which that part of the peritoneum, carried be- fore the testicle in its descent to the scrotum, is obhterated from its connection with the general cavity. The portion of perito- neum intervening between this point and the scrotum, usually degenerates into cellular tissue; it may, however, remain as a distinct cord, or even as a pervious tube. In the female subject, the round ligament enters the internal ring in place of the sper- matic cord, and also carries before it a pouch of peritoneum, but only for a short distance; the diverticulum, which it forms, is called the canal of Nuck. Direct Inguinal Hernia commences in the internal ingui- nal fossa in a triangle, called the triangle of Hesselbach, formed by the external edge of the rectus muscle, Poupart's ligament, and the obliterated umbilical artery; it carries before it the perito- neum which forms the sac of the hernia, the transversalis fascia, the conjoined tendon, (this, however, it sometimes splits, and passes through, instead of pushing before it,) the spermatic fascia, the superficial fascia, and the skin; it then descends towards the VISCERAL CAVITY. 155 scrotum. The epigastric artery and the spermatic cord, are both left on the outer side of this form of hernia. Oblique Inguinal Hernia commences in the external in- guinal fossa, and from that derives its peritoneal sac ; the internal inguinal ring entered, it pushes before it the infundibuliform fascia, and when in the canal, the cremaster muscle; at the ex- ternal ring, the spermatic fascia, the superficial fascia, and the skin ; it then descends towards the scrotum. In this form of hernia, the spermatic cord is beneath, and behind the tumor formed by it; the epigastric artery is on the inside, the reverse of its position in direct hernia. Oblique hernia, from its size and long existence, may so enlarge and drag upon the internal ring, as to bring it behind the external ring, and thus assume the appearance of a hernia primarily direct. The artery, of course, retains its relative position. When the portion of peritoneum, carried before the testicle in its descent, has not been obliterated, and the intestine passes into the sort of tube thus left, j£ is called a congenital hernia. When this tube is partially obliterated, and admits the intestine into its upper part only, it pushes down behind that portion which has formed the tunica vaginalis testis, and is called an encysted her- nia. Inguinal hernia rarely occurs in the female, but all the various forms have been noticed; in females, the hernia descends into the labia pudendi. DISSECTION II. VISCERAL CAVITY. In opening the abdomen, a thin peritoneal lamina, extending from the umbilicus to the liver, will be seen ; this is the broad ligament of the liver; in the free border of this, is a round cord of considerable size, called the round ligament, being the obliter- ated umbilical vein of fcetal life. These should be examined, at this time, as so good an idea of them cannot be obtained after their division. The abdomen is new to be opened, by incising longitudinally and transversely, whatever of the anterior parietes remains, and reflecting the flaps thus made. 156 ANATOMY OF THE ABDOMEN, ETC. The Visceral Cavity being exposed, it will be remarked that the intestinal tube, with its various divisions and convolutions occu- pies, apparently, the whole of the abdomen, the only viscus attract- ing attention at the first glance being the liver. The intestines will be found partially covered, superficially, with a membranous flap or apron; at times this is crumpled up, (so to speak,) and lies a confused mass, occupying but a small space; it may, however, always be spread out; it is called the great omentum. Occupying the upper part of the cavity, and in close apposition to the dia- phragm, will be seen the liver; partly covered by the liver, and filling the left side, is the stomach, behind which may be found the spleen. Below the stomach, and stretching across the spine, is the pancreas. From the stomach may be traced the small in- testine ; near the union of this with the stomach the surrounding parts will often be found discolored by bile which, after death, transudes through the walls of the gall-bladder. The small intestine occupies the central part of the visceral cavity and the pelvis; by running it through, from its commence/nent, we shall find that it joins the large intestine, or colon, in the right inguinal region. The large intestine ascends on the right side, covering in the kid- » ney, and is called the ascending colon; it crosses the abdomen at its upper part, under the name of the transverse colon, descends upon the left side, covering in the left kidney, as the descending colon to the left inguinal region, where it forms several folds, called the sigmoid flexure, and then dipping into the pelvis be- hind the bladder becomes the rectum. All the viscera, so far as they can be seen, as well as the walls of the abdomen, will be found covered with a thin, shinino- mem- brane, called the peritoneum; this facilitates the movements of the various organs, which are by no means inconsiderable, the position of the body influencing very greatly the position of the viscera. They have, notwithstanding, been located in regions, and though the boundaries of these are merely arbitrary, and are used only in the most general way as indicating the organs within their limits, allusion is constantly being made to them. It will be found convenient to indicate these regions by striugs, which should be stretched in the directions about to be enumerated, viz: two vertical lines from the most dependent portion of the cartilages of the eighth ribs to the centre of Poupart's ligament; a transverse line corresponding to the summits of the ilium, and another to the most dependent portion of the true ribs. PERITONEUM. 157 We thus have three zones, each subdivided into three regions. The three in the upper zone are, laterally, the right and left hypochondriac, in the centre the epigastric. In the middle zone, laterally, the right and left lumbar, and in the centre the umbilical. In the lower zone, laterally, the right and left inguinal, and in the centre the hypogastric. By handling the abdominal contents, the student can satisfy himself that the right hypochondriac region contains the liver, the left the spleen, and part of the stomach, whilst the epigastric contains a part of both the stomach and the liver ; the lumbar regions contain the kidneys on either side ; the umbilical the small intestines ; the right inguinal region contains the caBcum, the left the sigmoid flexure; the hypogastric region contains the bladder and rectum, and, in the female, the uterus. PERITONEUM. The Peritoneum is a serous membrane. Considered in its simplest form, a serous membrane is a hollow sac, into which a viscus protrudes itself, and thus, whilst getting a covering itself, lies within another covering of the same membrane, reflected from its own walls. We have only to consider this sac as large enough to admit of many viscera protruding into it, and we form an idea of the peritoneum; some of the viscera it merely passes over, without investing them on all their sides, and all of them are, in reality, outside the membrane. The folds made by the perito- neum, either in its reflections from the viscera which it has in- vested, or in passing from one organ to another, constitute means of support, and hold them in their proper places; these in cer- tain instances are improperly, though very conveniently, called ligaments, in others omenta, and in still other instances mesente- ries; besides supporting the organs, they contain the various vessels and nerves destined to the different parts. The great omentum consists of two folds of the peritoneum, which de- scend from the larger curvature of the stomach, covering in the small intestines, then doubling upon itself, it returns to be attached to the trans- verse colon; it therefore consists of four thicknesses; they are not, how- ever, easily separable. The great omentum contains a variable amount of fat, is sometimes perforated with holes, and is not unfrequently gath- ered up in a mass near the stomach. The lesser omentum is the fold extending between the smaller curvature of the stomach and the liver; it contains the portal vein, hepatic artery 158 ANATOMY OF THE ABDOMEN, ETC. and ducts; its left side is continuous with the oesophagus, but its right forms a free margin, beneath which the finger may be passed into the cavity of the peritoneum behind the stomach; this passage is called the foramen of Winslow. The gastro-splenic omentum passes from the outer border of the stomach to the spleen, and contains the splenic vessels. The mesentery proper is that fold of the peritoneum which holds down the small intestine, and which is attached posteriorly to the front of the spine; it is about four inches wide, and between its two layers, besides a considerable amount of fat, are the arteries, veins, and nerves of the small intestine, also the lymphatic vessels and glands, called the mesenteric glands. The transverse meso-colon is the mesentery of the transverse colon, and its medium of connection with the posterior wall of the abdomen. The meso-rectum and meso-ccecum are similar folds connected with the rectum and caecum. The meso-caecum is of such length as to permit great mobility to the caecum, though it is usually described as closely bound to the iliac fossa. I have seen a left inguinal hernia of the caecum. The complications of the peritoneum are not easily compre- hended, and it is only after a good deal of thought and repeated examination that they can be fully understood. In tracing the continuity of this membrane from above downwards, the student beo-ins at the liver, where he will perceive that it is prolonged from the under surface of that viscus on to the vessels. " From the liver it may be followed along the vessels, one layer before and the other behind them, forming the lesser omentum, to the upper border of the stomach. At the stomach the two layers enclosing the vessels separate, one going before and the other behind it; but beyond that viscus they are applied to one another to form the great omentum. After descending in contact in that fold to the lower part of the abdomen, they may be traced in it backwards and upwards, and may be seen to separate to enclose the transverse colon, like the stomach, and then to continue to the spine, giving rise to the transverse meso-colon. At the at- tachment to the spine the two companion layers will be found to separate, one passing upwards and the other downwards. The ascending layer is continued in front of the pancreas and the pillars of the diaphragm, and blends with the peritoneum on the posterior aspect of the liver. The descending layer may be fol- lowed from the transverse maso-colon along the middle line of the spine, over the duodenum, the aorta, and vena cava, till it meets DUCTS, VESSELS, AND NERVES, ETC. 159 with the artery to the small intestine, along which it is continued to form the mesentery, turning over the intestine and back to the spine along the other aspect of the vessels. From the root of the mesenteric artery the peritoneum descends to the pelvis, and partly covers the viscera in that cavity ; thus it surrounds the upper part of the rectum, and attaches this viscus to the abdom- inal wall by the meso-rectum ; next, it is continued forwards be- tween the rectum and the bladder, or between the rectum and the uterus, where it forms a pouch; thence it passes over the back and sides of the bladder. Lastly, the serous membrane is continued to the inguinal region, where it forms the fossae, before alluded to (p. 154), and it can be traced upwards on the anterior wall of the abdomen and the diaphragm, to the rest of the mem- brane on the upper surface of the liver." * The peritoneum may also be traced in a horizontal direction. Beginning at the umbilicus, it may be followed outwards to the large intestine, which it fixes to the abdominal wall by the meso- colon, over the kidney to the middle line, along the vessels to the small intestine, round the intestine and back to the spine along the other aspect of the vessels, and so outwards over the large intestine of the opposite side, to the parietes of the abdomen and the umbilicus. DUCTS, VESSELS, AND NERVES OF THE ABDOMINAL CAVITY. By raising the edge of the liver and drawing the intestines downwards, the biliary ducts, situated in the lesser omentum and lying between the two peritoneal layers forming the pillar of the foramen of Wlnslow, may be examined. From the duodenum a duct of variable size can be traced towards the liver; this is the ductus choledochus communis; it divides as it approaches the liver into two branches, one of which goes to the neck of the gall-bladder, and is called the cystic duct, the other going to the transverse fissure of the liver, the hepatic duct; they are accompanied by the hepatic artery and portal vein. The veins of the portal system may be found by pushing the viscera and search- ing for them in the regions to which they belong; it is impossible to dissect them without making special preparation for so doing. The Portal Vein or System is composed of those vessels ♦ Demonstrations of Anatomy. G. V. Ellis. London, 1857. 160 ANATOMY OF THE ABDOMEN, ETC. which return the blood from the chylopoietic viscera; they are the Inferior Mesenteric, Splenic, Superior Mesenteric, Gastric. The inferior mesenteric vein returns the blood from the rectum, sigmoid flexure and ascending colon, terminating in the splenic vein. The superior mesenteric vein returns the blood distributed by the supe- rior mesenteric artery; it ascends in company with that vessel, and be- hind the pancreas unites wi£h the splenic vein. The splenic vein commences in the spleen by several branches, which, uniting, form a large trunk that passes behind the pancreas, receiving the gastric veins from the stomach and duodenum. The union of this with the superior and inferior mesenteric veins forms the portal vein. The portal vein lies in the lesser omentum, between the biliary ducts and hepatic artery; it ascends to the transverse fissure of the liver, where it divides into two branches, one for the right and the other for the left lobe. The arteries of the various abdominal viscera all come from the abdominal aorta; the nerves from the pneumogastric and from the sympathetic ganglia. Their dis- section is oue of considerable difficulty, owing to the mobility of the viscera and the constant necessity of changing their position, so as successfully to expose the different trunks. The aorta should first be found at the point where it perforates the diaphragm, then, by removing the peritoneum, each artery, as it presents itself, is to be followed out by such means as the dissector's ingenuity will suggest. The nerves will some of them be exposed with the arterial trunks which they accom- pany; a detailed dissection of them is rarely accomplished; being composed of plexuses proper to each organ, they are usually made the subject of special dissec- tions. More than tracing, to some slight extent, the connection of these plexuses with the principal ganglia of the sympathetic, can hardly be expected. The stu- dent therefore need not be disappointed if he is unable to verify those paragraphs marked with an asterisk. The nervous plexuses of the abdomen may be enumerated as follows: Solar, Superior Mesenteric, Phrenic, . Aortic, Supra-renal, Inferior Mesenteric, Gastric, Renal, Hepatic, Spermatic, Splenic, Hypogastric. In searching for the coeliac axis, which lies behind the stomach, we shall come down upon the Solar Plexus, encircling the coeliac axis, covering the aorta, and spreading out in all direc- DUCTS, VESSELS, AND NERVES, ETC. 161 tions; it receives from both sides the greater splanchnic nerves (p. 106), and branches from the pneumogastric and phrenic nerves. The solar plexus contains a number of ganglia, the principal one of which is called the Semilunar, and it is the radiation of the nerves from this which gives the plexus the name of solar. From this plexus arise those branches that form the phrenic and supra-renal plexuses, and which may also be seen at this stage of the dissection. The Abhominal Aorta commences at the aortic opening of the diaphragm, and, descending on the left side of the vertebral column, terminates by dividing into the two common iliac arteries. The CtKLiAC Axis is the first large trunk given off by the abdominal aorta. The phrenic arteries are normally the first, but they are extremely irregular in their origin, and as often arise from the celiac axis as from the aorta; they are two in number, and ascend obliquely outwards, ramifying on the under surface of the diaphragm; their inosculations with other arteries are very numerous, and they send a branch to the supra-renal capsule on both sides. The coeliac axis is a short, but large trunk which arises close to the diaphragm and quickly divides into three branches, the gastric, hepatic, and splenic. Each of these branches con- veys the plexus of nerves "destined for the organ to which it is distributed, and it may be seen surrounding the artery as a sort-of sheath. The coeliac axis may be wanting, its branches originat- ing directly from the aorta: or it may give off but two branches, the gastric and the splenic, the hepatic coining from some other source, as, for instance, the superior mesenteric or aorta. The gastric artery is distributed to the smaller curvature of the stomach; it joins it near the oesophagus, to which it gives some ascending branches, whilst others pass round the cardiac extremity to the vasa brevia of the splenic artery; its terminal branch unites with the pyloric branch of the hepatic. The hepatic artery curves up towards the liver, and is* in close relation with the hepatic duct and portal vein; near the pylorus it gives off a pyloric branch to the lesser curvature of the stomach, where it inosculates with the gastric, also the gastro-duodenalis, which supplies the stomas" and duodenum; the gastro-duodenalis divides into the gastro-epiploica dextra, which goes to the larger curvature of the stomach and anastomoses with the splenic, and into thepancreatico-duodenalis, supplying the duode- num and pancreas, and anastomosing with the superior mesenteric. The hepatic at its termination divides into two branches which enter the trans- 11 162 ANATOMY OF THE ABDOMEN, ETC. verse fissure of the liver and separate to its right and left lobe. A small branch, the cystic, is given off by one of these to the gall-bladder. Acces- sory hepatic arteries are frequently found, usually coming from the gastric artery. The splenic artery is the largest branch of the coeliac axis; it supplies the spleen, pancreas, and stomach; it passes outwards in a tortuous man- ner, behind the pancreas, and divides into numerous terminal branches which penetrate the hilus of the spleen; the splenic vein is in close relation- ship with it. It reflects several small branches to the great end of the stomach which are called vasa brevia, and a single large branch passes along the greater curvature of the stomach, under the name of gastro-epiploica sinistra, anastomosing with a branch from the hepatic. Numerous small twigs are given off to the pancreas. The Superior Mesenteric Artery arises from the front of the aorta just below the coeliac, sometimes in connection with that trunk. A portion of this artery at its commencement is cov- ered in by the pancreas, to which it sends a small branch; it divides into numerous branches, which, placed parallel to each other, descend between the two layers of the mesentery, and then by a series of vascular arches, rarely if ever exceeding three in number, supply the small intestine from the duodenum to its ter- mination in the colon; these arches anastomose so freely with each other, that the circulation of any one point can never be inter- rupted by the compression of the intestinal folds. Besides sup- plying the small intestine, the mesenteric artery sends a separate division called the ileo-colic to the csecum and termination of the ileum ; another single division supplies the ascending colon, and is called the colica dextra; a third branch supplies the transverse colon, being called the colica media; these three trunks anasto- mose together by their terminal branches, and the last named inosculates with the colica sinistra, a branch of the inferior me- senteric, which supplies the descending colon and sigmoid flexure, " and so completes," says John Bell, " the great mesenteric arch, one of the most celebrated inosculations in the whole body, that of the circle of Willis hardly excepted." * These several branches of the mesenteric artery are accompa- nied by the nerves which constitute the superior mesenteric plexus; they can be found, together with several ganglionic masses, at the commencement of the artery which they surround, and may be traced back to the solar plexus; these nerves supply the pan- creas and intestinal tube. DUCTS, VESSELS, AND NERVES, ETC. 163 In the intervals of the branches of the mesenteric vessels nu- merous lymphatic glands are lodged; these are called the mesen- teric glands; the chyliferous vessels of the small intestine pass through these to reach the thoracic duct; these glands are often enlarged by disease. The Inferior Mesenteric Artery arises about two inches below the superior, also from the front of the aorta; it inclines to the left, and by a series of arches supplies the descending colon under the name of colica sinistra, forming large and free anasto- moses with the colica media of the superior mesenteric ; a second branch passes to the sigmoid flexure, and is called the sigmoid artery, and its terminal branch goes to the mesentery of the rec- tum, under the name of the superior hemorrhoidal artery; these three branches anastomose freely with each other. * The front of the aorta between the mesenteric arteries is cov- ered by the aortic plexus; this connects with the solar plexus, and also unites with the lumbar ganglia, situated upon the sides of the vertebra;; from it passes off the inferior mesenteric plexus, which, accompanying the artery of that name, supplies the parts to which it is distributed. The intestines should now be removed. To do this the rectum is to be tied and divided; the large intestine should then be dissected from the meso-colon close to the intestinal wall, and the small intestine separated from the mesentery in a similar manner, tying and dividing it just below the duodenum; they are then to be set aside for further examination, and kept immersed in water. The Renal Arteries are given off at right angles from the sides of the aorta just below the origin of the superior mesenteric • the right is given off lower down, and is shorter than the left; they divide into several terminal branches to enter the kidney at its hilus; occasionally they penetrate through the sides of the organ. The aorta sometimes gives off two, three, and even four, renal arteries to one kidney, and they often vary on the two sides of the body. * The renal plexus lies upon the renal artery, and is composed of branches from the solar and aortic plexuses; the inferior splanch- nic nerve (p. 106) also terminates in this plexus. Ganglia of various sizes occur in it, and its branches ramify upon and in the substance of the kidney. A small branch from the side of the aorta just above the renal 164 ANATOMY OF THE ABDOMEN, ETC. artery goes to the supra-renal capsule, and is called the Supra- Renal Artery. The capsule usually receives a branch from the renal artery also. The Spermatic Arteries are two long and slender branches given off from the front of the aorta just below the origin of the renals; occasionally they arise by a common trunk; sometimes there are two upon one side, and their origin may be from the renal artery. They pass downwards beneath the peritoneum, crossing the ureter and external iliac artery, to the internal in- guinal ring, and then accompany the spermatic cord to the testes. In the female these arteries are called the ovarian, and instead of passing out of the abdominal cavity, they dip into the pelvis, and pass up between the layers of the broad ligament of the uterus to the ovaries. The length of these vessels will be accounted for, when it is remembered that the testicle descends at the close of intra-uterine life to the scrotum from the lumbar region, and that the ovary, during pregnancy, is lifted with the uterus above the umbilicus; it is therefore for the purpose of accommodating these displacements of the organs to which they are distributed. * The spermatic plexus accompanies the spermatic arteries; it is formed by branches from the renal and aortic plexuses. The spermatic veins accompany the spermatic arteries in a part of their course; they are formed by the union of several venous branches which surround the spermatic cord, and ascend as single trunks, the right to enter the vena cava and the left to join the left renal vein. It has been attempted to explain the more fre- quent occurrence of varicocele upon the left side, by the less direct entrance of the blood from the vein of that side into the general circulation. The abdominal aorta will be found to terminate in two branches at the level of the fourth lumbar vertebra called the Common Iliac Arteries ; these diverge, and divide, opposite the union of the sacrum with the os innominatum, into external and in- ternal iliac arteries; the former courses along the brim of the pelvis to pass out beneath Poupart's ligament, and become the artery of the lower extremity; the latter dips into the pelvis to supply the viscera it contains. In negroes and in old sub- jects, the common and external iliac arteries are often curved DUCTS, VESSELS, AND NERVES, ETC. 165 and tortuous. Lymphatic glands will be found along their course. At the point of the aorta's bifurcation a small artery is given off called the Sacra Media ; it descends on the middle line of the sacrum, giving off short branches upon either side in its course towards the coccyx, where it tenninates. It sometimes arises from the left common iliac. The lumbar ganglia, forming part of the continuous chain of the ganglia of the sympathetic, which extends from the head to the coccyx, should now be dissected; their connection with the ante- rior branches of the spinal nerves can also be traced. The gang- lia will be found much larger in size than those in the tho- racic region, they also lie closer together; upon the right side they are covered in by the vena cava, on the left they rest upon the vertebra? along the edge of the psoas muscle. The branches which communicate with the anterior spinal nerves are of consid- erable length and accompany the lumbar arteries, passing be- neath the fibrous bands from which the psoas muscle arises. * These ganglia give origin to the hypogastric plexus which lies upon the anterior surface of the sacrum and last lumbar vertebrae, and distributes its branches to the viscera of the pelvis. The Lumbar Arteries are four in number and correspond to the intercostals of the thoracic aorta. They arise from the posterior aspect of the aorta, those of the right side being the longest and covered in by the vena cava, and, passing over the bodies of the vertebra?, dip beneath the psoas muscle and divide into two branches, one of which goes to the spinal cord and spinal muscles, whilst the other continues its course forwards to the abdominal muscles. The first lumbar artery passes under the pillar of the diaphragm, and along the edge of the last rib; the last lumbar passes along the crest of the ilium. The lumbar arte- ries of the opposite sides sometimes arise by a common trunk, which sends out its branches laterally; two arteries of the same side are sometimes conjoined at their origin. The External Iliac Vein is the continuation of the femo- ral vein, and will be found accompanying the external iliac artery; at Poupart's ligament it lies on the inside of the artery, but gradu- ally gets beneath it; it is joined by the internal iliac vein, which 166 ANATOMY OF THE ABDOMEN, ETC. returns the blood from the penis and pelvic viscera. These two veins form the common iliac veins, which, uniting upon the right side of the aorta, form the Vena Cava Inferior ; this ascends along the right side of the abdominal aorta, receiving in its course the lumbar veins, which accompany the lumbar arteries, the left being the longest; the renal, which lie in front of the renal arteries, the left renal crossing the aorta and being the longest; the supra- renal, which, however, sometimes terminate in the renal; the phrenic, returning the blood from the diaphragm, and the hepatic, which empties the blood from the portal system and the hepatic artery. The phrenic and hepatic veins cannot be seen until the liver is removed. The spermatic veins are long and slender veins accompanying the spermatic arteries; the right spermatic enters the front of the vena cava, the left spermatic enters the left renal vein ; these return the blood from the scrotum and testicles. The vena cava passes out of sight beneath the liver, where it traverses a groove destined for it, and passing through a special opening in the diaphragm, penetrates the pericardium and terminates in the right auricle of the heart. The vena azygos major and minor (p. 106) originate from the lumbar veins, and pass up beneath the diaphragm to unite with the vena cava superior. DISSECTION III. INTESTINAL tube. The intestines must be washed before they can be examined, but it should never be done until they are opened; this may be accomplished by the scissors, or by a special instrument called an enterotome; the section should be made along the line of attachment of the mesentery. The portion of the alimentary canal known as the Intestines, extends from the stomach to the anus, and is divided into the small and large intestine. The small intestine extends from the pylorus to the caacum, the large from the cajcum to the anus; they differ from each other in structure as well as size, the first being of uniform calibre, and the second much larger, and of a sacculated and irregular outline. INTESTINAL TUBE. 167 The small intestine, about twenty feet in length, is arbitrarily divided into three portions, duodenum, jejunum, and ileum. The duodenum is the first twelve inches beyond the stomach; the jejunum is the first two fifths of the remaining portion ; the lower three fifths constitute the ileum, which terminates in the caecum. The large intestine, about five feet in length, is divided into the cacum, or caput coli, the ascending, transverse, and descending colon, the sigmoid flexure, and the rectum. Attached to the cae- cum is a small, tapering, tubular appendage, from three to six inches in length, held in its place by a mesentery proper to it; it is usually tortuous, and about the size of a pipe-stem ; it com- municates with the interior of the caecum through a small orifice, and is called the appendix vermiformis caci. Two or three long- itudinal bands run the whole length of the large intestine ; they are about half an inch wide, and being shorterjthan the canal itself, give to its walls a sacculated character. To form a proper idea of the ileo-csecal valve, the caecum and a portion of the ileum should be inflated and dried; then cutting a window in the side, its arrangement may be seen. The entrance of the ileum into the large pouch of the cascum is protected by a valve, called the ileo-cacal, to prevent regur- gitation ; it is formed from the mucous coat of the caecum, and, seen from within that part of the intestine, appears as a trans- verse, elliptical opening, formed by two lips, which, when closed, overlap each other, and which any distension of the caecum can only close more effectually. The walls of the intestines are composed of three coats, viz: peritoneal, muscular, and mucous. The peritoneal coat com- pletely surrounds the small intestine, its two layers meeting to form the mesentery. With the exception of the caecum, which it wholly invests, and furnishes with a mesentery, it only partially covers the large intestine ; passing over its anterior portion, and then being reflected on to the parietes of the abdomen, it leaves the posterior wall in direct contact with the iliac fascia. Attached to the peritoneal surface of the large intestine, small fatty bodies are sometimes seen, hanging off in a fringe-like manner; they vary in number and size, and are called appendices epiploica. If the peritoneum be peeled off from the intestine, the muscular coat, consisting of pale, transverse fibres, will be seen beneath it; 168 ANATOMY OF THE ABDOMEN, ETC. in the large intestine these are chiefly collected in the longitu- dinal bands characteristic of that part of the tube. The mucous coat is continuous throughout the whole alimentary canal. In the upper part of the small intestine it lies in a series of trans- verse folds, called valvula conniventes; these gradually disappear in the ileum. In the large intestine it is thrown into sharp ridges, corresponding to the constrictions of its sacculi. The cel- lular tissue connecting the mucous and muscular coats, and which may be demonstrated by stripping off the mucous mem- brane, is sometimes described as a fourth coat, called the fibrous, or sub-mucous. The intestines are furnished with certain Gland-, which may be seen upon the surface of the mucous membrane. The solitary glands are white, rounded, and slightly prominent bodies, scat- tered over the surface of both large and small intestine, in the former being found chiefly in the caecum. The follicles of Lieber- kuhn, found also in both large and small intestine, consist of little follicles with a minute orifice, hardly perceptible. The ngminated or Peyer's glands belong chiefly in the ileum, and uecur only in the small intestine ; they are of an oblong shape, have a granu- lated aspect, and are placed opposite the attachment of the mesentery ; the number and position of these patches varies, but there is almost always a large one near the termination of the ileum in the caecum. The velvet-like surface of the mucous membrane of the small intestine is made up of villi, minute pro- cesses in which commence the lacteals, and which a re only dis- tinctly visible with the assistance of a lens. The duodenum, not having been removed with the rest of the intestine, will be found in situ; it is the first ten or twelve inches of the tube beyond the stomach; it has no mesentery, and lies beneath the peritoneum, which only covers its anterior surface ; the direction taken by it gives it the shape of a horseshoe, the convexity of which looks towards the right side ; the head of the pancreas occupies the concavity, and its duct, as well as that of the liver, opens into it through the posterior wall. A form of gland, called Brunner's glands, is peculiar to this portion of the intestine; they are scattered in great numbers throughout its whole extent, and give the mucous surface a sort of granular as- pect. THE SPLEEN. 169 The Stomach is an expanded portion of the alimentary canal, between the oesophagus and duodenum. The oesophagus, after passing through the diaphragm, terminates by gradually dilating into the stomach. That portion of the stomach expanding to the left of the oesophagus is called its cardiac extremity, and that at the opposite end the pyloric extremity. The superior curved border is called the lesser curvature, and the inferior border the greater curvature; to these borders are attached respectively the lesser and greater omentum. The stomach varies in size, accord- ing to the individual, and the degree of distension by its contents, and consequently varies somewhat in the position it occupies ; it is, however, always in relation with the diaphragm, the abdom- inal parietes, and the liver, and by a fold of the peritoneum, called the gastro-splenic omentum, with the hilus of the spleen. The left pneumogastric nerve 'may be traced upon the anterior surface of the stomach, and the right upon its posterior surface. The stomach is to be removed by dividing it at the oesophagus, close to the dia- phragm,^and at the duodenum, in such a way as to leave behind that portion per- forated by the ductus choledochus communis; it should then be laid open along the greater curvature. The coats of the stomach, as in the rest of the alimentary canal, are three in number, viz : peritoneal, muscular, and mucous. The peritoneal coat envelops it entirely. The muscular coat is made up of numerous and well-marked fibres, arranged in longi- tudinal, circular, and oblique directions. The mucous coat is movable, and slides upon the muscular; if not fully distended it will therefore be thrown into rugae by the contraction of the lat- ter ; its surface is characterized by a sort of granulated appear- ance due to the follicles with which it is provided. At the py- loric extremity the mucous membrane fornis a valve called the pylorus; this is sometimes a complete ring, at others merely two crescentic folds; the muscular fibres beneath form a sort of sphincter, and the entrance to the duodenum may be closed by their contraction. The color and condition of the mucous coat is variously modified by the contents of the stomach and by post- mortem changes. THE SPLEEN. The Spleen is situated beneath the cartilages of the ribs, at the cardiac extremity of the stomach, with which it is connected 170 ANATOMY OF THE ABDOMEN, ETC. by the gastro-splenic omentum ; it is also held in contact with the diaphragm by a suspensory peritoneal ligament; its connections, however, are not very strong, and it may easily be torn out from its position with the fingers. It is completely invested by peri- toneum, closely adherent, and presents externally a smooth sur- face, convex externally, and concave internally. The upper end of the spleen is larger than the lower; the posterior border is blunt and rounded, the anterior comparatively sharp, and con- taining one or more notches. The concavity of the spleen admits the arteries, and gives exit to the veins, and that portion in rela- tion with these is called its hilus. The splenic artery, of large size, divides at its entrance into several branches ; the vein, also of large size, joins the portal vein, by a trunk common to it with the gastric and inferior mesenteric veins. Its nerves are derived from the solar plexus. A section of the spleen exhibits a reticulated parenchyma of very elastic nature, from the meshes of which large quantities of blood may be squeezed or washed. In its tissue, pearly bodies are sometimes seen, not unlike miliary tubercles; these are called the corpuscles of the spleen. The spleen varies in weight from two drachms to forty pounds; its average is from five to seven ounces. Its size may be averaged at five inches in length by three or four in width, and one to two inches thickness. Within the folds of the peritoneum, in the neighborhood of this viscus, it is not uncommon to find supple- mentary spleens, small rounded bodies, varying from the size of a pea to that of a pigeon's egg; in structure, these are similar to that of the spleen proper. THE PANCREAS. The Pancreas is an irregularly shaped viscus, some six inches in length, lying transversely upon the vertebra?, behind the stomach. It is a conglomerate gland, the substance of which is of a pale color, and broken up into easily separated lobules. It is divided into a head and body, the head being that portion em- braced by the duodenum. A portion of the gland surrounds the mesenteric vessels, and this prolongation is sometimes called the lesser pancreas. By making a longitudinal incision into the sub- stance of the pancreas, and carefully separating the lobules, a THE LIVER. 171 delicate white duct will be exposed; this is the pancreatic duct; it commences at the extremity of the gland, and gradually in- creasing in size by the accession of small branches, makes its exit at the head of the viscus, and, in company with the hepatic duct, penetrates obliquely through the walls of the duodenum at the posterior part of its perpendicular portion, opening into its in- terior by a common orifice with the bile duct. Occasionally it has a separate aperture, and there may be a second, supplemen- tary duct. THE LIVER. By lifting the cartilages of the right side with the chain-hooks, and by lifting and drawing the liver in different directions, its attachments and relations may be suc- cessively observed and studied. The Liver is a conglomerate gland, and the largest viscus in the body; it weighs from three to four and a-half pounds; its color is a reddish-brown, and its surface is covered with peritoneum, except in such intervals as are left between the layers reflected from the viscus to the parietes of the abdomen, and which con- stitute the ligaments that hold it in place. It is in relation supe- riorly and anteriorly with the diaphragm and abdominal parietes ; inferiorly with the stomach and transverse colon, and posteriorly with the diaphragm and vertebral column, the aorta, and vena cava. The liver is held in its place by the following ligaments :— Broad, or Suspensory, Right and left Lateral, Round, Coronary. The broad, or suspensory ligament, with its accompanying round liga- ment, was noticed at the time the abdomen was opened, and their divided ends will now be seen lying upon the superior surface of the liver at its anterior margin. It is a thin, double layer of peritoneum, extending from the posterior to the anterior border of the liver, and attached to the dia- phragm and anterior wall of the abdomen, as far as the umbilicus. The round ligament is a white fibrous cord, the obliterated umbilical vein of foetal life, occupying the lower border of the broad ligament; it passes under the anterior border of the liver into a longitudinal fissure of its under surface, terminating in the walls of the portal vein. The lateral ligaments are peritoneal folds, passing from the diaphragm to each extremity of the liver, the left being the longest of the two. The coronary Jigament is situated along the posterior border of the vis- cus, between the two lateral ones. The two reflections of the peritoneum 172 ANATOMY OF THE ABDOMEN, ETC. composing it, leave a considerable space between them, so that this por- tion of the liver is in immediate contact with the diaphragm, and con- nected with it by firm cellular attachments. To remove the liver, these different ligaments are to be divided; it is then to be carefully dissected from the diaphragm, cutting across the vena cava where it perfo- rates that muscle, and preserving a portion in connection. Precaution should be taken not to tear the liver or perforate the diaphragm, accidents which are liable to occur. The duodenum, or that portion of it left expressly on account of its con- nections with the liver, should also be removed with the ducts which connect it to the gall-bladder and under surface of the liver. Removed from the body, the liver presents superiorly a surface uniformly convex, and divided into two portions by the broad ligament, called right and left lobes, the right being much the larger of the two. It can now be seen that the posterior border is rounded, and the anterior sharp and thin; the posterior border is notched by the vertebral column; the anterior border is also notched at the point of its separation into two lobes, and some- times also in front of the gall-bladder. The under surface of the liver is very irregularly concave, and is broken up by fissures and lobes. A fissure containing the round ligament, divides the under surface, as the broad ligament did the upper, into its right and left lobes ; the left lobe is comparatively thin and smooth, the right is much thicker; upon it are situated three other lobes, viz : thelobus Spigelii, caudatus, and quadratus. The lobus Spigelii is a triangular-shaped, partially detached lobe, sur- rounded by fissures, and placed in the middle of the posterior part of the liver. The lobus caudatus is a sort of ridge, extending from the lobus Spigelii towards the middle of the right lobe; it is not usually well defined. The lobus quadratus is the portion of the right lobe intervening between the gall bladder and the fissure of the round ligament, and in front of the fissure at which enter the portal vein and hepatic artery. The transverse fissure is the most important of all the fissures of the under surface of the liver; it occupies nearly the centre of the organ, and is the depression where the portal vein and hepatic artery enter, and the hepatic duct makes its exit. It is sometimes called the hilus, and as being the entrance or porta of the liver, gives a name to the vein that finds ad- mission at this point. The hepatic duct is the most anterior of the vessels of the transverse fissure, the artery is next, and the vena porta most pos- terior. The longitudinal fissure, containing the round ligament, joins the trans- verse nearly at a right angle; the substance of the liver sometimes crosses this fissure, and converts it partially into a canal. THE LIVER. 173 The fissure of the ductus venosus is that portion of the longitudinal fissure posterior to the transverse; it lies between the lobus Spigelii and the left lobe, and contains a rounded cord, continuous with the round ligament, which terminates in the vena cava; this cord being the obliterated duc- tus venosus, which, during foetal life, conveys directly to the cava a por- tion of the blood of the umbilical vein. The fissure of the vena cava lies between the lobus Spigelii and the right lobe; it is occupied by the vena cava, and is sometimes converted into a canal. On laying open the vena cava, the orifices of the hepatic veins will be seen, this being the point at which they discharge their blood to enter into the general venous circulation. The fissure of the gall bladder is the fossa in which that receptacle rests. From the preceding description, it will be seen that the liver has five lobes, five fissures, five ligament*, and five vessels, which may be thus tabulated :— Lobes. Fissures. Vessels. Ligaments. Right, Transverse, Hepatic Duct, Coronary, Left, Longitudinal, Hepatic Artery, Broad, Spigelius, Ductus Venosus, Hepatic Veins, Right Lateral, Caudatus, Vena Cava, Portal Vein, Left Lateral, Quadratus. Gall Bladder. Vena Cava. Round. The Gall Bladder is a pyriform sac, the fundus of which extends just beyond the anterior margin of the liver; the neck is directed towards the transverse fissure, and terminates in the cystic duct. The coats of the gall bladder are three in number, viz : peritoneal, cellular, and mucous. The peritoneal coat only partially invests it, its posterior surface being in direct contact with the liver, and connected to it by the cellular coal. The mucous coat is very finely reticulated, and stained deep brown by the bile which tinges all the coats, and gives the bladder a green- ish hue; towards the neck, the mucous membrane is thrown into prominent folds, which form a sort of valve at the point of its union with the cystic duct. The cystic duct, about an inch in length, joins with the hepatic duct of the liver two inches distant from the transverse fissure at which it emerges ; their union forms the ductus choledochus com- munis, a tube of some three inches in length, which terminates in the duodenum as already described. The gall bladder is merely a reservoir of superfluous bile, and the ductus choledochus con- veys the bile from it as well as directly from the liver. 174 ANATOMY OF THE ABDOMEN, ETC; The hepatic duct, the hepatic artery, and portal vein, are sur- rounded by a loose areolar tissue which accompanies them in their ramifications, and which is called Glisson's capsule. This capsule may be seen constituting, as it were, the fibrous skeleton of the organ, by tearing the liver, or by stripping off the closely adher- ent peritoneal coat; it surrounds the minute granules or acini, of which this fracture or incision shows the liver to be made up. The hepatic veins are closely adherent by their parietes to the substance of the liver, and cannot, therefore, contract, as the loose areolar tissue surrounding the portal veins permits those vessels to do ; in a section of the liver, consequently, these may be easily distinguished from each other. The portal vein will be found collapsed, and accompanied by an artery and a duct; whilst the hepatic vein will remain open and uncontracted, and is unaccom- panied by any other vessel. The liver is supplied with blood from the hepatic branch of the coeliac axis; the portal vein also conveys its current through the organ, and, collecting the impure blood of the hepatic arteries, terminates in the hepatic vein; this empties into the vena cava inferior, and so completes the hepatic circulation. The hepatic plexus of nerves, derived from the solar plexus, accompanies the hepatic artery in its subdivisions. The liver also receives branches from the phrenic and pneumogastric nerves. DISSECTION IV. THE SUPRA-RENAL CAPSULES. The supra-renal capsules are to be sought for beneath the peritoneum, high up in the lumbar region, on each side of the spinal column. The Supra-renal Capsules are small, flat, crescentic bodies, covered in by peritoneum and surmounting the kidneys, to which their concave surface is sometimes directly applied; an interval not unfrequently, however, exists between the two organs. They are of a yellowish color, and easily obscured amongst the fat and cellular tissue of the surrounding parts. The right capsule rests upon the diaphragm between the kidney and the liver, oftentimes THE KIDNEYS. 175 as closely adherent to one as the other of these organs. The left capsule also rests upon the diaphragm, beneath the pancreas and spleen. For so small organs they are largely supplied both with nerves and arteries, the former constituting a supra-renal plexus derived from the solar plexus, the latter being branches of the aorta, and the phrenic and renal arteries; the supra-renal vein terminates sometimes in the inferior cava and sometimes in the renal vein. Upon section, they are seen to be made up of an external or cortical substance, of a yellow color, and an inter- nal or medullary substance, dark and semi-fluid; an internal cavity is sometimes described, but it is a question if it be not the result of post-mortem degeneration. One or two instances of entire absence of the supra-renal capsules have been reported, and in the foetus they have been found united together across the vertebral column. THE KIDNEYS. The kidneys occupy the lumbar region on each side of the vertebral column, lying beneath the peritoneum, enveloped in fat and cellular tissue. To expose them, both the peritoneum and lumbar fascia must be removed and the ureter traced downwards, either in part or the whole of its course. The Kidneys are oval-shaped organs of a deep red color, and smooth surface, convex externally and concave towards the ver- tebral column ; the concave border at its central part presents a longitudinal fissure called the hilus; at this point the renal ar- tery enters and the vein and ureter emerge. The Ureter is the excretory duct which conveys the urine to the bladder; it is of the size of a pipe-stem, except at its com- mencement, where it is dilated and forms part of what is called the pelvis of the kidney. The ureter is of a bluish-white color and of a firm fibrous texture, and is lined within by a thin mucous mem- brane ; it passes downwards upon the psoas muscle, behind the peritoneum, crosses the external or common iliac artery, and dips down behind the bladder to enter it at its base. The ureter is sometimes double, either in a part or the whole of its length. The ureter should be divided midway between the kidney and the bladder; then the vein and artery being cut across, the kidney may be easily and without injury torn from its bed by the fingers. A longitudinal incision along its convex margin should divide the kidney in such a way that it may be opened and its interior ex- posed, without its two halves being separated at the concave border. 176 ANATOMY OF THE ABDOMEN, ETC. The kidney is about four inches long, two wide, and one in thickness; it weighs about four and a half ounces; its posterior surface is flatter than its anterior, and it is invested with a special capsule, which the nail of the thumb and fore-finger may easily detach from its surface. Internally, it is composed of two distinct structures and an irregular-shaped cavity, called the pelvis. That portion surrounding the pelvis is made up of cones, called pyramids of Malpighi, the apices of which are pointed towards the centre of the organ ; they are composed of a congeries of straight tubes called tubuli uriniferi. The apices of the pyramids are called papilla, and are covered by a thin mucous membrane, perforated by orifices, through which the tubuli discharge the urinary secretion; they are surrounded by a sort of " prepuce," so to speak, also covered by a thin mucous membrane, and which is called the calyx, or infundibulum, of the pyramid; together, these form irregular cavities, the dilatations of which correspond to the depressions between the papillae; the ureter opens from the general cavity which they form, and their mucous surfaces are continuous. The external, or cortical portion of the kidney, surrounds the bases of the pyramids, and penetrates irregularly between them; it is composed of the tubuli convoluted amongst minute vascular ramifications. The kidney is a very vascular organ and receives its blood through the renal artery, a large branch of the aorta, affording an excellent illustration of the law that the size of an artery is in proportion, not to the size of the viscus to which it is distrib- uted, but to the activity of its functions. The renal vein empties into the inferior vena cava ; and the nerves, which are abundant, are received from the renal plexus, derived from the solar plexus and the lesser splanchnic nerve. The relative position of the vessels at the hilus permits the right kidney to be distinguished from the left after their removal from the body; the renal vein is the most anterior, the artery is behind the vein, and the ureter posterior to them both. The kidneys not unfrequently present deviations from their normal shape and position ; sometimes they are united into one body across the vertebral column, forming what is called a horse- shoe kidney; occasionally one is wanting. They may be found placed much lower in the lumbar region than usual, and have THE DIAPHRAGM. 177 even been found in the pelvis. They are usually firmly placed in their positions, but in certain instances a degree of mobility has been noticed, appreciable by palpation during life, and con- stituting what is called a floating kidney. THE DIAPHRAGM. To get a good view of the diaphragm, a large block is to be placed under the loins in such a way as to elevate the base of the thorax. The peritoneum must be thoroughly removed from its surface; and if the thorax has not yet been opened, it will be readily stripped off by the forceps and fingers. The Diaphragm is a muscular plane separating the abdomen from the thorax; it arises from the sternum by short and separated fibres, which leave a triangular interval between them, covered only by peritoneum on one side and the pleura on the other; from the superior border and internal surface of the last six ribs by ser- rations which indigitate with the transversalis muscle of the abdo- men (p. 150) ; also from a fibrous arch called the ligamentum arcuatum externum, extending from the tip of the last rib to the base of the transverse process of the first lumbar vertebra, and curving over the quadratus lumborum muscle; it further arises from a smaller fibrous arch called the ligamentum arcuatum inter- num, which stretches from the termination of the preceding to the body of the second lumbar vertebra, curving over the psoas magnus muscle; and also from the bodies of the second and third lumbar vertebrae by tendinous fibres which are common to it and the anterior common ligament of the vertebra?. From this circumference the fibres converge to be inserted into the cenfral tendon, a glistening expansion in the centre of the muscle, the metallic brilliancy of which has given it the name of the speculum of Van Helmont. The above description is of what is called the larger muscle of the diaphragm. The lesser muscle consists of two fleshy bundles arising by separate tendons from the bodies of the lumbar vertebrae, the right one being the larger and the longer, and inserted into the central tendon. They are also called the pillars or crura of the diaphragm, and the left one is sometimes wanting. The right pillar crosses the left in such a way as to divide the interval between them into two separate parts; the lower one, parabolic in shape, gives passage to the aorta, vena azygos, and thoracic duct; the upper, elliptical in 12 178 ANATOMY OF THE ABDOMEN, ETC. shape, transmits the oesophagus and the pneumogastric nerves. In the central tendon is a third opening, the largest of all, which transmits the vena cava inferior. The diaphragm, on the thoracic side, is covered by the pleura and the pericardium, the fibrous layer of which blends with the central tendon. The diaphragm is supplied by the phrenic nerves, and is nour- ished by the phrenic arteries and by the musculo-phrenic branch of the internal mammary artery. The Receptaculum Chyli, ordinarily the commencement of the thoracic duct (p. 107), lies close beside the right pillar of the diaphragm, and between the aorta and vena cava; it usually rests upon the second lumbar vertebra, and consists of a thin, semi-transparent, membranous sac, oblong and irregularly shaped; it is ordinarily empty, and may be best demonstrated by insuffla- tion with the blow-pipe from the duct above. The thoracic duct may sometimes, though rarely, be traced below the receptaculum, which, in that case, becomes merely a dilated portion of the duct The greater and lesser vena azygos, described at page 106, may sometimes be better seen in this connection than at any other period of the dissection. Both these veins usually pass through the aortic opening of the diaphragm, but they not unfrequently perforate its fibres at the sides of the pillars. ANATOMY OF FEMORAL HERNIA. Inasmuch as the dissection of the internal abdominal muscles, and the parts in relation to them, will destroy many of those connected with the anatomy of femoral hernia, it is desirable to proceed to the examination of it before they are disturbed. The knees of both legs should be bent so as to bring the soles of the feet in appo- sition, with the heels approached to the nates; an incision, six inches in length, is to be made through the skin from the centre of Poupart's ligament down the thigh, and the integument reflected to either side; this will expose the superficial fascia. Femoral hernia is most advantageously studied upon a female subject. The superficial fascia, like that of the abdomen, with which it is continuous, consists of two layers; it contains several small arterial branches, all arising from the femoral artery, just below Poupart's ligament. The superficial epigastric artery passes upwards, between the two layers of the fascia, towards the umbilicus, and has already been seen, in part, during the dissection of inguinal hernia. ANATOMY OF FEMORAL HERNIA. 179 The superficial external circumflex artery passes outwards towards the anterior superior spinous process and crest of the ilium. The superficial external pudic artery passes inwards to be distributed to the integument of the penis and scrotum, or to the labia in the female. Several cutaneous nerves will be found lying in the superficial fascia ; they are small, and derived from the anterior crural and genito-crural branches of the lumbar plexus. Enlarged lymphatic glands are usually found both in and be- neath the superficial fascia; they are connected with the lym- phatics of the lower extremity, and their efferent ducts enter the abdomen through the saphenous opening. The superficial fascia may be removed by dissecting it away from the fascia lata beneath; a portion of it should, however, be left for the present, around the point where the saphenous vein penetrates the thigh. The deep external pudic artery, arising from the femoral, lies between the superficial and the deep fascia; after a short course it penetrates the latter, and then, reappearing from beneath it, is distributed to the external organs of generation. It is the largest of the superficial arteries. The Internal Saphenous Vein, commencing on the back of the foot, ascends along the inside of the thigh to join the femoral vein«J that part of it exposed in the present dissection, lies be- tween the superficial and the deep fascia, and receives several small veins from the neighborhood; it passes through an opening in the deep fascia, called the saphenous opening, and then unites with the femoral vein. A portion of the superficial fascia, per- forated by small orifices, which give entrance to the efferent ducts of the lymphatic glands imbedded in it, and hence called the cribriform fascia, covers in the saphenous opening. The deep fascia, or fascia lata, is a strong fibrous sheath invest- ing the whole lower extremity. The saphenous opening, a little to the inside of the middle of the thigh, and an inch below Pou- part's ligament, ovoid in shape, and in outline resembling the reversed Greek letter sigma, divides the fascia lata into two parts, iliac and pubic. The iliac portion is on the outer side, and is connected with the whole length of Poupart's ligament; from this attachment it passes outwards and downwards, its edge forming the outer margin of the saphenous opening, and consti- tuting what is called its falciform border. This border may be 180 ANATOMY OF THE ABDOMEN, ETC. followed round, underneath the saphenous vein, and will be found to unite with the pubic portion of the fascia lata on the inside of the opening; it also blends with the superficial fascia, so that they are only separable by dividing them with a knife. The pubic portion of the fascia lata is inserted into the spine of the os pubis, and, passing under Poupart's ligament, into the pectineal line, where it becomes continuous with the fascia investing the psoas and iliacus muscles within the abdomen. In attaching itself to the pectineal line under the name of Hey's ligament, it helps to form Gimbernat's ligament, the triangular termination of Poupart's, which, widening at its inner end, forms the concave border directed towards the femoral vessels, known by that name. Reverting to the abdominal cavity, and removing the perito- neum, it will be seen that the transversalis fascia, and the fascia covering the psoas and iliacus muscles unite, externally to the vessels, and form a continuous fold, closely connected with Pou- part's ligament; where the vessels pass out the fasciae separate and surround them, terminating about two inches below the ligament, by blending with their areolar sheath; the sort of funnel thus made, and through which they pass downwards into the thigh, is called the infundibuliform fascia. It is plain, therefore, that whilst the fold, externally, protects that part of the space between Poupart's ligament and the os innominatum from a hernial protru- sion, it is liable to occur at the point where the vessels oblige the fasciae to separate. The space between Poupart's ligament and the os innominatum is called the crural arch ; it is occupied, externally, by the psoas and iliacus muscles, between which passes the crural nerve.; next the muscle comes the iliac artery, then the iliac vein, between which and the inner termination of Poupart's ligament is a space called the crural ring. The crural ring is about half an inch wide, and is filled with the sub-peritoneal cellular tissue, and a lymphatic gland, which form a partition, called the septum crurale. The greater size of the crural arch in females than in males, arising from the greater breadth of their pelvis and the lesser develop- ment of the soft parts, makes the crural ring a more decided opening in them, and explains why they are more subject to her- nia at this point. The vessels and the crural ring are all inclosed in the infundibuliform fascia, but are separated from each other ANATOMY OF FEMORAL HERNIA. 181 by septa. By dividing Poupart's ligament, and turning it care- fully to either side, these septa may be seen, one between the ar- tery and vein, and one between the vein and the crural ring. The space between the crural ring and the point at which the saphenous vein joins the femoral, is called the crural canal; its ante- rior wall is the transversalis portion of the infundibuliform fascia, with the falciform border of the iliac side of the fascia lata; the posterior wall is formed by the iliac portion of the infundibuli- form fascia and part of the pubic side of the fascia lata ; its ex- ternal wall is the septum, forming the division between the canal and the femoral vein, and its internal wall, Gimbernat's and Hey's ligament. The epigastric artery is in close relation to the upper and outer side of the crural ring, and the obturator ar- tery, when given off from the external iliac, dips downward along its outer and inferior edge ; in a certain number of instances this artery arises from a trunk common to it and the epigastric, in which case it curves around the ring to descend upon its inner side ; the obturator vein may follow the same course. It will be seen that this distribution of the artery exposes it greatly to be wounded in dividing the crural ring, in an operation for stran- gulated femoral hernia ; observation, however, having shown that the point of constriction is ordinarily in the fascia lata and not in the ring, the danger which formerly was so properly dreaded, has disappeared before a more enlightened practice. The spermatic cord is separated from the crural ring by Pou- part's ligament. The preceding description shows us that a hernia taking place at the crural ring, finds little or nothing to oppose its protrusion at the saphenous opening, and thus become external; and although whilst in the canal it must be much constricted, from the unyield- ing nature of its walls, it may, after emerging, expand into a tumor of considerable size. The blending of the superficial fascia with the fascia lata, just below the saphenous opening, prevents the hernia from descending beyond that point, and arrived at this obstruction, it turns upwards towards Poupart's ligament. The practical importance of this fact, in connection with attempts at taxis, is of course obvious. The intestine, in descending, must carry before it the following coverings; first, the peritoneum, then the septum crurale, and 182 ANATOMY OF THE ABDOMEN, ETC. that portion of the infundibuliform fascia which, forming the an- terior wall of the canal, is perforated by the saphenous vein, these two latter constituting what is called the fascia propria of the hernia; and, externally, to the saphenous opening, the cri- briform fascia, the superficial fascia, and the integument. the lumbar plexus. The dissection of the lumbar plexus presupposes the removal of the peritoneum and cellular tissue in the lumbar region; the nerves composing it are mostly small in size, and though liable to be divided by the dissections already made, their ori- gin and a portion of their course'ttay always be demonstrated. The Lumbar Plexus is formed by the communications of the anterior branches of the five lumbar nerves; the posterior branches being distributed to the muscles of the back. The principal trunks are the following, viz:— Musculocutaneous, Crural, External Cutaneous, Obturator, Genito-crural, Lumbo-sacral. The musculo-cutaneous nerve, coming from the first lumbar nerve, crosses the quadratus lumborum muscle obliquely, to reach the middle of the crest of the ilium, where it pierces the transversalis muscle, and divides into two branches, the abdominal and the scrotal; the abdominal supply- ing the muscles and integument of the abdomen, and the scrotal, joining the spermatic cord in the male, and the round ligament in the female, at the external inguinal ring, to the integument of the scrotum or labia majora. The external cutaneous nerve, coming from the second lumbar nerve, crosses the iliacus internus muscle obliquely, to reach the anterior supe- rior spinous process of the ilium, where it passes underneath Poupart's ligament, and is distributed to the integument of the gluteal region, and outside of the thigh. The genito-crural nerve, coming from the second and third lumbar nerves, runs down upon the psoas muscle, and divides into a genital and a crural branch. The genital branch enters the internal abdominal ring, and accompanies the spermatic cord or round ligament to the integument of the groin; the crural descends along the outer border of the external iliac artery, enters the sheath of the femoral vessels, and is distributed to the integument of the front of the thigh. The crural nerve, coming from the second, third, and fourth lumbar nerves, is the largest branch of the lumbar plexus; it pierces the psoas muscle, then passes downwards between it and the iliacus, and about an inch below Poupart's ligament, divides into numerous branches hereafter to be described. THE LUMBAR PLEXUS. 183 The obturator nerve, coming from the third and fourth lumbar nerves, passes down among the fibres of the psoas muscle, and behind the iliac vessels, along the brim of the pelvis to the upper and inner part of the ob- turator foramen, which it perforates, to be distributed to the adductor muscles of the thigh. The lumbosacral nerve, from the fourth and fifth lumbar nerves, de- scends into the pelvis over the base of the sacrum, and unites the lumbar with the sacral plexus. The dissection of these nerves will have exposed the internal abdominal muscles. The Psoas parvus Muscle lies in front of and upon the psoas magnus; it arises from the sides of the bodies of the last dorsal and first lumbar vertebrae, forming a small belly that ex- pands into a broad, flat tendon, which, losing itself in the fascia of the iliacus muscle, is inserted into the pectineal line and ilio- pectineal eminence in a manner calculated to prevent the con- tractions of the psoas magnus from compressing the iliac vessels in the crural ring. This muscle is frequently wanting; when absent the fascia iliaca is more developed, and supplies its place. The Psoas magnus Muscle is a long muscle, lying parallel to the vertebral column, and arising from the sides of the bodies of the last dorsal, and four upper lumbar vertebrae, and from the transverse processes of all the lumbar vertebrae; it forms the border of the true pelvis laterally, and is inserted, in common with the iliacus internus, into the trochanter minor of the femur, and an inch or more of the shaft of the bone below it. That portion arising from the transverse processes is sometimes dis- tinct from the rest of the muscle in its whole course. The Quadratus Lumborum is covered in by the anterior layer of the lumbar fascia; this removed, it will be found to arise from the last rib, and the transverse processes of the upper, four lumbar vertebrae, and to be inserted into the posterior part of the crest of the ilium. If the muscle is divided, and the two ends reflected, the middle portion of the lumbar fascia will be ex- posed. The Iliacus internus Muscle arises from the transverse process of the last lumbar vertebra, the crest and concavity of the ilium, and the anterior part of the capsule of the hip-jointi and in common with the tendon of the psoas magnus, is inserted into the lesser trochanter of the femur. The insertions of neither 184 ANATOMY OF THE ABDOMEN, ETC. of these muscles can be satisfactorily seen until after the dissec- tion of the muscles of the anterior femoral region. The External Iliac Artery, with its accompanying vein, lies along the inner border of the psoas muscle ; it has no branches till it reaches Poupart's ligament, where it gives off two, and sometimes three. The epigastric artery has been already noticed (p. 151), but may now be more particularly observed as to its origin; this is usually close to Poupart's ligament, but it may be found at a very considerable distance either above or below it; it frequently furnishes the obturator artery. The circumflexa ilii artery arises from the outer side of the artery, and winds along Poupart's ligament and the crest of the ilium; it lies between the internal oblique and transversalis muscles, and breaks up into numer- ous branches, some of which supply the muscles, whilst others inoscu- late with the ilio-lumbar artery, a branch of the internal iliac; these anas- tomoses principally take place beneath the iliacus muscle, and if that be divided and detached from the ilium, they will be brought into view. The obturator artery nominally arises from the internal iliac, but in a certain number of cases it arises from the external iliac by an indepen- dent origin, or by a trunk common to it and the epigastric; it then de- scends to reach the upper and inner part of the obturator foramen, and passes out through an opening in the obturator membrane, to be distrib- uted externally to the pelvis; as it perforates this membrane it is often joined by a small branch given off from the internal iliac, which preserves the normal origin and course of the artery. It will be desirable at this period to turn the subject over. If the previous dissections have been accomplished, this can be done without embarrassing those engaged upon the lower extremity. The parts connected with the region of the back will be found described in Part Second, Dissection V. DISSECTION V. ANATOMY of the perineum. The dissection of the perineum interfering with that of other parts of the body, should consequently be made in common, the dissectors mutually agreeiug to sus- pend operations until it is accomplished. It can be done advantageously only on the male subject; the peculiarities of the female perineum will be found at p. 187. The legs being flexed, the thighs are bent upon the trunk, and the nates made to project over the edge of the table, preserving the position by one or two turns of a cord carried round the right knee, then under the table to the left knee, and finally made fast by again attaching it to the right k.nee. The subject being ANATOMY OF THE PERINEUM. 185 thus placed, the scrotum and testicles should be lifted on to the pubes, and kept out of the way by hooks or pins; the rectum is to be distended with cotton wool tow, or similar material, and when well filled the anus should be made to project by pressing it downwards from within the pelvis. The perineum being washed and shaved, is then ready for dissection. An elliptical incision, commencing at the root of the scrotum, its long diameter corresponding to the median line, should include the anus, and be limited by the coccyx posteriorly; the integument is then to be dissected upon all sides towards the anus. The Perineum is an important surgical region, bounded on each side by the tuberosities of the ischia, in front by the arch of the pubes, and behind by the coccyx; in other words, its bounda- ries are those of the inferior strait of the pelvis. Immediately beneath the skin, where it becomes continuous with the mucous surface of the anus, the fibres of the sphincter ani will present themselves, pale in color, and indistinctly char- acterized. Elsewhere, a layer of fat covers in the deeper parts of the perineum ; laterally, between the anus and the ischia this is considerable in amount, and fills a large space, called the ischio- rectal fossa. The external hemorrhoidal artery traverses the ischio-rectal fossa; it is an offset from the internal pudic artery, itself a branch of the internal iliac, lying under the ramus of the ischium, and is distributed to the sphincter and levator ani muscles and to the lower part of the rectum. Farther in front, the internal pudic gives off the superficial perineal artery; this passes forwards to the scrotum, giving off in its course a branch called the trans- versalis perinei, which crosses the perineum upon the transversus perinei muscle. These arteries are accompanied by small branches from the internal pudic and perineal cutaneous nerves. The internal pudic nerve is an offset from the sacral plexus, which takes the course of the internal pudic artery, and divides into a superior and inferior branch, the former going to the penis, the latter to the scrotum and perineum. The perineal cutaneous nerve comes from the lesser sciatic, and ascends along the ramus of the ischium to supply the scrotum and the integument below the penis. The preceding dissection will have exposed several muscles, small in size, but, with a single exception, sufficiently well marked to be readily recognized. The Sphincter Ani is an elliptical-shaped muscle, surround- 186 ANATOMY OF THE ABDOMEN, ETC. ing the anus. It arises from the tip of the coccyx, and is inserted an inch or more in front of the anus in common with two other muscles, hereafter to be described, into a fibrous spot called the perineal centre. Deeper in the pelvis, but continuous with this muscle, will be seen the circular fibres proper to the rectum itself; these constitute the sphincter ani internus; they blend with, and become lost in the lower part of the levator ani muscle, which comes down from each side of the pelvis, and surrounds the gut, as will hereafter be seen on making a section of the pelvic cavity. The Transversus Perinei Muscle is a small bundle of fibres, occasionally wanting on one or both sides, which arises from the tuberosity of the ischium, and is inserted into the peri- neal centre. A slip, arising in common with this, sometimes passes forwards, and becomes blended with the accelerator urinae ; this is called the transversus perinei alter. The Erector Penis arises from the tuberosity and ramus of the ischium by a strong tendon, and forming a round, fleshy belly, is inserted on the side of the penis into the strong fascia investing the corpus cavernosum. The Acceleratores Urine lie upon the corpus spongiosum of the penis; arising from the perineal centre and the raphe that separates them, their fibres diverge to encircle the penis, the pos- terior being inserted into the-ramus of the pubes and ischium, the middle surround the corpus spongiosum, and the anterior, spreading upon the corpora cavernosa, are inserted into their investing fascia. By dividing the muscles inserted into the perineal centre, and reflecting them, the bulb of the corpus spongiosum penis will be exposed, and, directly behind it, a strong fascia named the triangular ligament, through which the membranous portion of the urethra passes. The Triangular Ligament, so called from its occupying the triangular space formed by the arch of the pubes, is the deep perineal fascia, extending from one ramus of the ischium and pubis to the other ; it is composed of two layers, the anterior of which unites with the superficial fascia in front of the anus, and the posterior, passing backwards, invests the membranous urethra and prostate gland. It furnishes one of the chief supports and means of resistance, to the superincumbent weight of viscera pressing down upon the perineum. ANATOMY OF THE PERINEUM. 187 The Transversus Perinei profundus Muscle lies between the two layers of this ligament; it arises from the ramus of the pubis and is inserted into the perineal centre. It frequently con- ceals the artery of the bulb, and Cowper's gland lies beneath it. The artery of the bulb is a branch of considerable size, arising from the internal pudic; it passes transversely inwards to the bulbous portion of the corpus spongiosum, to which it is distrib- uted. Cowper's Glands, one on each side, are small bodies, the size of a pea, placed at the side of, and a little behind the bulb of the corpus spongiosum; they secrete a fluid carried by a duct into the bulbous portion of the urethra. Their size, and the na- ture of the locality in which they exist, often renders them diffi- cult to demonstrate. The erector penis muscle is to be dissected away on one side, from the ramus of the pubes and ischium, keeping close to the bone; this will permit the dissection of the internal pudic artery. The removal of the erector penis shows the strong tendinous nature of that muscle at its origin from the bone ; the other ex- tremity being connected with the corpus cavernosum, it forms one of the chief supports of the penis, and is called the crus penis. The Internal Pudic Artery may now be sought for, and will be found lying under the edge of the ramus of the ischium. This artery is one of the terminal branches of the internal iliac; it passes out at the greater sacro-ischiatic foramen, crosses the spine of the ischium, and enters the pelvis again by the lesser sacro-ischiatic foramen to reach the ramus of the ischium, about an inch in front of the tuberosity; it passes along this to the symphysis pubis, where, under the name of the dorsalis penis, it runs the length of the organ from which it takes its name, to ter- minate in the glans. The muscles of the female perineum differ little, except in name, from those of the male. The constrictor vagina surrounds the orifice of the vagina, arising from the perineal centre, and inserted into the corpus cavernosum of the clitoris; it corresponds to the accelerator urinae. The transversus perinei is inserted into the sides of the con- strictor vaginae. 188 ANATOMY OF THE ABDOMEN, ETC. The erector clitoridis arises from the ramus of the ischium, and is inserted into the sides of the corpus cavernosum of the clitoris. The artery of the bulb is distributed to the vagina. DISSECTION VI. interior of the pelvis. To examine the interior of the pelvis it is necessary to detach one of the inferior extremities with the corresponding os innominatum. To do this, the symphysis pubis is to be cut through; the sacro-iliac articulation of one side being found, and its anterior ligaments divided, by making the edge of the table a fulcrum, and forcibly separating the divided pubes, the dislocation of the ilium from the sacrum will be effected; the common iliac and the branches of the internal iliac, are to be divided, and the pelvic viscera separated from their lateral attachments; then cut- ting through the sacro-sciatic ligaments and the gluteus maxim us muscle and skin externally, the limb will be separated, and one half the pelvis remain undisturbed. The disadvantage of this method is that one side is necessarily sacrificed. The sacrum may be sawed through upon the median line instead of dislocating the ilium; the glutei muscles are then left uninjured upon both sides, but the pelvis is not left in so favorable a condition for advantageous dissection. We are now able to see the position of the pelvic viscera, and to study the folds of peritoneum which invest them. It will be seen that the rectum is covered with peritoneum, and held in its place along the middle of the sacrum by a mesentery called the meso-rectum; from the rectum the peritoneum passes over the bladder, leaving a fold between called the recto-vesical fold, and which sometimes forms a tight band or cord-like edge on its posterior surface. If the subject be a female one, we shall have the uterus between the bladder and rectum, and there will then be two folds, the recto-uterine and the vesico-uterine. The lateral reflections of the peritoneum form the false ligaments which sustain the pelvic viscera. It will be noticed that the lower part of the rectum and a large part of the lower half of the bladder have no peritoneal coat, that membrane merely cover- ing them in, and then being reflected to the sides of the pelvis. The point at which it is reflected from the bladder to the anterior abdominal parietes should be especially examined, to notice the fact that it is possible to perforate the bladder above the pubes without implicating its serous coat. In the female subject INTERIOR OF THE PELVIS. 189 the uterus is almost, if not wholly, covered by the peritoneum, and the space between the peritoneal cavity and the vagina, at its union with the neck of the uterus, is so trifling that the former might easily be perforated, in operations about the vagina and os uteri. The bladder is held in its place by five false ligaments; the two posterior being that portion of the peritoneum forming the recto- vesical fold of each side: the two lateral, corresponding with the obliterated umbilical artery and the vas deferens in its passage to the base of the bladder; and the superior being a fold of peri- toneum projected between the umbilicus and the summit of the bladder by the urachus, an obliterated foetal canal. Besides these the bladder has four true ligaments; two anterior, formed by the pelvic fascia reflected from the pubes to the neck and front of its anterior surface, and two lateral, formed by the recto- vesical fascia, or that portion of the pelvic fascia covering the levator ani and reflected from it to its sides. In the female subject, the peritoneum is reflected from the uterus to the sides of the pelvis in such a manner as to form a septum between it and the bladder, which is called the broad liga- ment. In the space between the division of the aorta into the iliac arteries, and spreading over the concave surface of the sacrum, is the hypogastric plexus of the sympathetic system, destined to the pelvic viscera; it is formed from the aortic plexus, and from branches of the lumbar nerves; it has but few ganglia, and those small ones. From this plexus originate the hemorrhoidal, vesical, prostatic, vaginal, uterine, and ovarian plexuses, supplying the parts indicated by their names, but only demonstrable by special dissections. Having verified these different relations and attachments of the pelvic viscera, the next step is to trace the arteries. The bladder should be inflated, and kept so by a string tied round the penis; it is then to be drawn by hooks to the side from which the os innominatum has been removed. The divided extremity of the ureter is to be sought for, and also the vas deferens; having found and isolated these, the peri- toneum is to be dissected off from the sides of the pelvis, and the arteries cleared from the surrounding cellular tissue, tracing them as they are one by one given off from the internal iliac and its divisions. The Internal Iliac Artery is a short trunk of large size, arising from the common iliac; it dips into the pelvis, keeping 190 ANATOMY OF THE ABDOMEN, ETC. close to its walls, and divides into an anterior and a posterior trunk. The artery lies upon the internal iliac vein and the lumbo-sacral nerve; the ureter crosses it and separates it from the peritoneum. The length of the internal iliac is subject to great variation, and its branches are often irregular as to their precise point of origin, sometimes arising without the separation of the vessel into two trunks; they may all be determined by the parts to which they are distributed. The anterior trunk gives off the following branches:— Superior Vesical, Obturator, Inferior Vesical, Ischiatic, Internal Pudic; and in the female subject, these two in addition :— Uterine, Vaginal. The hypogastric artery, at the close of intra-uterine life, becomes oblit- erated to within an inch and a half of its commencement, leaving an im- pervious cord; the portion remaining pervious gives origin to the superior vesical arteries. The superior vesical arteries are three or four in number, arising at inter- vals from the stump of the hypogastric, and are distributed to the upper part of the bladder; the most inferior of the branches is sometimes called the middle vesical artery. The inferior vesical artery arises from the internal iliac, in common with a branch to the rectum; it is distributed to the base of the bladder and vesicular seminales and prostate. The branch to the rectum is called the middle hemorrhoidal; it supplies the lower part of the rectum, and the vagina in the female, anastomosing with the superior and inferior hemor- rhoidal arteries; it sometimes arises from the internal pudic. The obturator artery, already referred to (p. 184), arises normally from the anterior division of the internal iliac; it passes forwards, accompanied by the obturator nerve which lies above it, to the upper part of the obtu- rator foramen, beneath the horizontal branch of the pubes, where it emerges from the pelvis and divides into its terminal branches. The obturator sends a small twig to the iliacus muscle, and another to the posterior sur- face of the pubes. The ischiatic artery is the largest branch of the anterior division of the internal iliac; it passes downwards, lying upon the sacral plexus of nerves, and leaves the pelvis just in front of the sciatic nerve through the greater sacro-ischiatic foramen, to be distributed to the muscles of the gluteal region and the back of the thigh. Within the pelvis it gives off small branches to the rectum and base of the bladder. The internal pudic artery is another branch of large size. It passes down in front of the ischiatic and emerges from the pelvis at the greater INTERIOR OF THE PELVIS. 191 sacro-ischiatic foramen, crosses the spine of the ischium and enters the pelvis again by the lesser sacro-ischiatic foramen to reach the r.imus of the ischium, along which it passes, giving off the perineal branches de- scribed at page 185, and terminating in the dorsalis penis artery. The uterine artery arising in the female from the anterior division of the internal iliac, passes between the layers of the broad ligament and reach- ing the neck returns to the fundus of the uterus, giving off branches to the surface and substance of that viscus; it is usually more or less tortuous, and anastomoses freely with the ovarian artery, a branch from the abdomi- nal aorta analogous to the spermatic of the male (p. 164). During preg- nancy the uterine arteries increase greatly in size, and become still more tortuous. The ovarian artery passes between the layers of the broad liga- ment, and, after many tortuous convolutions, penetrates the ovary. The vaginal artery seldom arises directly from the internal iliac; given off frequently from the uterine or from the middle hemorrhoidal, it passes down in the posterior wall of the vagina to anastomose, near its termina- tion, with the corresponding artery of the other side. Both the uterine and vaginal arteries give small branches to the bladder and rectum. The posterior trunk of the internal iliac gives off the following branches: — Ilio-Lumbar, Lateral Sacral, Gluteal. The ilio-lumbar artery passes upwards and then outwards, beneath the external iliac, to the crest of the ilium; it there divides into two branches, one of which supplies the iliacus internus by ramifications between the muscle and the bone, forming numerous anastomoses with the circum- flexa ilii; the other branch passes upwards to supply the psoas and quad- ratus lumborum. This artery is analogous to the lumbar arteries; it varies considerably in its precise point of origin. The lateral sacral artery passes down upon the side of the sacrum to the coccyx, inosculating with the sacra media. It sends branches through the anterior sacral foramina to the terminal portion of the spinal cord, and these, finally emerging at the posterior sacral foramina, supply the posterior surface of the sacrum. The gluteal artery is a short thick trunk, the apparent continuation of the posterior division of the internal iliac; it passes out of the pelvis above the border of the pyriformis muscle, with its accompanying vein and the superior gluteal nerve, to be distributed to the gluteal muscles, as will be seen in the description of that region. The superior hemorrhoidal artery, a branch of the inferior mesenteric, will be found distributed to the upper part of the rectum, lying between the two layers of peritoneum constituting the meso-rectum, and anastomosing with the middle and external hemorrhoidal arteries. 192 ANATOMY OF THE ABDOMEN, ETC. All of the arteries just described are accompanied by veins, which, with the exception of the hemorrhoidal and spermatic veins, empty into the internal iliac vein. The hemorrhoidal veins, more or less connected with the other veins, especially those about the neck of the bladder, empty into the inferior mesenteric vein, which terminates in the vena porta. The spermatic and ovarian veins terminate, the right in the vena cava, the left in the renal vein. The nerves of the pelvic cavity are numerous, important, and many of them of large size. The lumbosacral and obturator nerves have been already de- cribed (p. 183) ; they are again seen at this stage of the dissec- tion, the former joining the sacral plexus, the latter passing out at the obturator foramen with the obturator artery. The Sacral Plexus is formed from the four anterior sacral nerves. The fifth sacral nerve terminates in the perineum, where it unites with the sixth, or coccygeal nerve, and is distributed to the side of the coccyx and coccygeus muscle. The sacral plexus is a broad, flat, nervous band lying upon the piriformis muscle; within the pelvis, it furnishes several visceral branches to the pelvic organs, which unite with the branches of the hypogastric plexus, and also muscular branches to the internal pelvic muscles; it then divides into the following branches, destined to external parts, viz :— Gluteal, Internal Pudic, Great Sciatic, Lesser Sciatic. These all pass out through the greater sacro-ischiatic foramen, and will be described in connection with the parts to which they are distributed. The pelvic fascia, covering in the obturator internus muscle, may be traced as a single layer from the brim of the pelvis as far as a white line stretching from the symphysis pubis to the spine of the ischium; at this line it'diyides into two layers, one of which continues over the rest of?the obturator muscle, and the other, under the name of the recto-vesical fascia, passes down to be attached to the side of the bladder and rectum. Between these two layers is the levator ani muscle. INTERIOR OF THE PELVIS. 193 The Levator Ani Muscle, a broad, thin plane of muscular fibres, forming, with its fellow, the floor of the pelvis, is compared by Bell to a pair of hands dipping down to hold up and sup- port the viscera, the simile being suggested by the funnel-shaped manner in which they embrace the pelvic contents. The muscle arises from the inner surface of the os pubis, from the white line constituting the point of separation between the obturator and recto-vesieal fascia, and from the spine of the ischium; it is in- serted into the lower part of the rectum, where its fibres become connected with those of the internal sphincter, and into the base of the bladder and the prostate gland. In the female, the levator ani is inserted into the sides of the vagina as well as the rectum. The two following muscles are very difficult of demonstration. They are to be sought for between the two layers of the triangular ligament, where they lie con- nected with the membranous urethra and pubic bones. The Compressor Urethra, or Guthrie's Muscle, con- sists of two transverse layers of muscular fibres, attached by nar- row ends on each side to the ramus of the pubes ; expanding at their central portion, one above and the other below, they em- brace the whole length of the membranous urethra. Wilson's Muscle, the existence of which has been doubted, is considered, when present, as a part of the preceding, and as being merely another attachment of its fibres. It arises, tendin- ous, from the under part of the symphysis of the pubes, and de- scends, fan-shaped, on each side of the urethra, to be inserted into the upper layer of the compressor. The pelvic viscera should now be removed, and in such a way as to leave the in- ternal inusclos and nerves of the pelvis uninjured; the arterial connections must be divided, and the rectum dissected up from the concavity of the sacrum. The penis should be removed with the viscera, detaching it from the arch of the pubes, by carrying the knife close to the bone. In the female, the vulva and anus should be included in an.elliptical incision, and carefully dissected away from the rami of the ischia and pubes. These parts should be laid aside for further examination. Within the pelvis will be noticed the bellies and origins of two muscles which have their insertions outside; these are the obtura- tor internus and the pyriformis. The Obturator Internus Muscle arises from the bone around the obturator foramen, and from the membrane which stretches across it; it forms a triangular belly, covered by the pelvic fascia, and which, tapering to a point, passes out of the 13 194 ANATOMY OF THE ABDOMEN, ETC. lesser sacro-ischiatic foramen, to be inserted into the digital fossa of the trochanter major. The Pyriformis Muscle arises from the sacrum, between the first and fourth anterior sacral foramina, from the greater sacro- sciatic ligament, and from a portion of the ilium, forming a trian- gular belly which terminates in a rounded tendon, and passing out at the sacro-ischiatic foramen, is inserted into the digital fossa of the trochanter major. The Coccygeus Muscle is a small collection of muscular-and tendinous fibres, arising from the spine of the ischium, and in- serted into the side of the coccyx; its lower border is connected with the levator ani. It is apt to be mutilated in the removal of the rectum and anus. DISSECTION VII. THE RECTUM. The pelvic viscera may now be examined, commencing with the rectum; this should be cleared from all extraneous tissue, but without separating it from its connections with the bladder, The Rectum is about eight inches in length; it follows a curved direction, corresponding to that of the sacrum, and gradu- ally increases in size, especially in old people, from its commence- ment to within an inch and a half of the anus. The last inch and a half is contracted, and follows a direction downwards and back- wards to its termination in the anus. Its anterior surface is in contact with the bladder and its appendages in the male, and the uterus and vagina in the female, the upper portion being separated only by the recto-vesical, or recto-uterine fold of the peritoneum, whilst the lower portion is in direct apposition, or separated only by cellular tissue; in the male subject this region is occupied by the prostate gland and vesiculae seminales. The rectum laid open along its posterior aspect, will display a thick mucous membrane lying chiefly in longitudinal folds; at the lower parts, these are called the columns of Morgagni, and are generally three in THE BLADDER. 195 number. The ftiuscular fibres are longitudinal and circular; the longitudinal cease at the lower part, and give place to the circu- lar fibres which form the internal sphincter. THE BLADDER. The rectum must now be removed. The ureter and vas deferens are to be fol- lowed to their terminations.. The peritoneum should be dissected from off the bladder. The Bladder, when distended, is of an ovoid shape, the sum- mit or superior end being the smaller ; it is connected with the penis by a somewhat funnel-shaped portion, called its neck. In the male, the neck is surrounded by the prostate gland; in the female, the place of this is supplied by cellular and muscular tis- sue. The summit of the bladder terminates in the urachus, the remains of a canal, called the allantois, which, during the early part of foetal life, connected the bladder and the umbilical aper- ture. In addition to the serous, the bladder has a muscular and a mucous coat. The fibres of the muscular coat are arranged both in a circular and a longitudinal manner; the circular fibres are chiefly found round the neck, and constitute what is called the sphincter vesica; the longitudinal ones are well marked, both in front and behind, and, from their office, are named, collectively, the detrusor urina. The mucous coat of the bladder is thrown into folds, or becomes smooth, according to the degree of its distension. At the lower and anterior part of its interior, is the orifice of the urethra, the aper- ture of which is partly closed by a small mucous projection, called the uvula vesica. By blowing through the ureters, their orifices will be demonstrated, as well as the obliquity with which they pene- trate the bladder. The triangle formed by these two orifices, and the orifice of the bladder, is called the trigonum vesica, and is made apparent by the greater adhesion of the mucous membrane to the parts beneath than elsewhere. Especially in a hypertrophied condition of the muscular coat of the bladder, two muscular bands proceeding from the orifices of the ureters may be seen, on lifting the mucous coat, converging towards the urethral orifice ; closely united with the sub-mucous cellular tissue, they cross each other at their point of convergence, and form the uvula vesicae ; they 196 ANATOMY OF THE ABDOMEN, ETC. then become continuous with the longitudinal ntuscular fibres of the urethra. They are called the muscles of the ureters, and serve to occlude the orifice of the ureters, and open the neck of the bladder. They were first described by Sir Charles Bell, and " more recently and correctly by G. V. Ellis, of University College, London. MALE ORGANS OF GENERATION.* VESICUX.*: SEMINALES AND PROSTATE GLAND. The vesiculse seminales lie^mbedded in a mass of cellular tissue at the base of the bladder; this is to be removed, and the prostate is also to be isolated from the veins and fascia investing it. The Vesiculse Seminales are two flattened, oblong bodies, situated on each side of the inferior surface of the bladder, closely adhering to it, and converging from a point near the termination of the ureters to meet at the base of the prostate gland. Each vesicle consists of a coiled tube, the convolutions of which are closely united to each other. The Vas Deferens, consisting of a firm, fibrous tube, lined internally with mucous membrane, commences at the epididymis of the testicle, and passes up with the veins and arteries com- posing the spermatic cord, to the internal abdominal ring; it then leaves the vein and artery to pass down into the pelvis, and, get- ting behind the bladder, descends between it and the rectum to the inner side of the vesicula seminalis ; it here becomes dilated, and assumes a somewhat sacculated condition, and ends by blend- ing with the vesicula, to form the ductus communis ejaculatorius, which, passing through the under surface of the prostate gland, terminates in the urethra. The Prostate Gland is a body shaped like a chestnut, which surrounds the neck of the bladder and the commencement of the urethra; its pointed extremity is directed forwards. It is invested by a dense fascia, and a very noticeable plexus of veins called the prostatic plexus, which communicates with the dorsal vein of the penis, and the hemorrhoidal veins of the rectum. The prostate is composed of two lateral lobes, the division of * The female organs of generation are described at the close of this dissection. THE PENIS. 197 which is not always well marked. The third lobe, described by Sir Everard Home, being the result of enlargement by disease of that portion of the gland situated below the urethra and behind the ducts of the vesiculae seminales, and which the absence of resistance permits to project in that direction more freely than elsewhere, is, with more propriety, described by Thompson as the posterior median portion. The normal dimensions of the prostate are an inch and a half transversely, an inch longitudinally, and three quarters of an inch vertically. " The prostate consists of organic muscular fibres, arranged in a circular manner around its long axis, through which passes the urethra. It has no claim, therefore, to be regarded as a gland at all, in the sense in which that term is used to classify certain structures in the human body, but rather as a muscular body permeated by urethral glands." * On section, the gland is very firm to the feel, and is of a reddish color. The orifices of its glands are numerous, and open into the prostatic part of the urethra. THE PENIS. The Penis, as has been already seen, is connected to the pelvic bones by the ligamentum suspensorium and the two crura formed by the erectores penis. It is composed of the corpora cavernosa, corpus spongiosum, and glans. These are covered with integument, loosely attached by cellular tissue, that portion of it which invests the glans being called the prepuce. The corpora cavernosa constitute the bulk of the penis; sepa- rating posteriorly, to join with the crura, they unite at the root of the penis, and are firmly connected together; they terminate anteriorly in a blunt extremity, covered in by, and closely united with, the glans. Flattened upon their superior surface, a slight groove receives the dorsal artery and vein and the dorsal nerve of the penis ; these all extend to the glans. The under surface of the corpora cavernosa is more deeply grooved to receive the corpus spongiosum; this commences at the root of the penis, in a dilated extremity called the bulb, which is embraced by the acce- leratores urinae, and, passing along the under surface of the corpora * Thompson on the Prostate. 198 ANATOMY OF THE ABDOMEN, ETC. cavernosa, expands at their termination, to form the glans penis. The urethra occupies the centre of the corpus spongiosum. The glans, being larger than the surrounding body of the penis, forms a projecting " shoulder," called the corona glandis, which is filled with sebaceous glands, called the glands of Tyson. It is covered with a delicate mucous membrane, reflected upon the inner side of the prepuce, and continuous with the external skin of the organ. The external orifice, or meatus of the urethra, opens in the glans by a vertical fissure, and, from the lower end of this, the mucous membrane forms a fold between the prepuce and the gland, called the frenum. The corpus spongiosum and the corpora cavernosa are invested by a dense elastic fascia, called the sheath of the penis. The in- ternal structure of both these bodies and of the glans is essentially the same ; it is what is called erectile tissue, being composed of venous and arterial ramifications; fibrous bands, called trabecula, passing in different directions, add strength to this tissue, which, upon section, has a spongy aspect, and is more or less filled with venous blood. The blood is supplied by the branches of the internal pudic artery, and returned by the vena dorsalis, which is joined by short branches, entering it upon the upper surface and at the root of the penis, and empties into the prostatic plexus. The urethra extends from the orifice of the bladder to the meatus of the glans, and is divisible into three portions : prostatic, membranous, and spongy. It should be exposed by laying it open with the scissors along the superior surface. The prostatic portion is that surrounded by the prostate gland. Upon the under surface of this portion is a projection, called the veru montanum, or caput galinaginis : the depression on each side of this is called the prostatic sinus, the floor of which is perforated by the orifices of the prostatic ducts; these may be demonstrated by squeezing the gland; this will force out the secretion through their apertures. At the anterior part of the veru montanum is an opening, called the sinus pocularis, and upon the sides of this the ejaculatory or seminal ducts have their opening ; their exist- ence may likewise be demonstrated by compressing the vesiculae seminales. The membranous urethra is that portion between the prostate and the bulb; it passes through the triangular ligament, and is THE TESTES. 199 less than an inch in length. It is surrounded by areolar tissue and veins, and by the compressor urethras, or Guthrie's muscle. The spongy portion of the urethra, surrounded by the erectile tissue of the corpus spongiosum, extends from the bulb to the meatus. In the bulb, the urethra forms a dilatation, and at this point may be found the two orifices of the ducts of Cowper's glands; a second dilatation occurs about an inch from the meatus, and is called the fossa navicularis. The mucous membrane of the urethra is thin and delicate, and is sometimes thrown into longi- tudinal folds; it has numerous follicular orifices, one of which, in the fossa navicularis, is of large size, and is called the lacuna magna. THE TESTES. The testes are contained in an envelop called the scrotum. They may, however, remain in the abdomen, or be arrested in the inguinal canal, instead of descending from the lumbar region to the scrotum, as they should at the close of intra-uterine life. In such cases, they are usually imperfect or small, " contrary to an old authority," says John Bell; " it having been said, ' that the testicles are seated externally for chastity's sake; for such live wights as have their stones hid within their body are very leche- rous, do often couple, and get many young ones.'" The Scrotum is composed of a tegumentary covering, and a fascia continuous with those of the abdomen and perineum ; it is divided into two compartments by a septum, the position of which is indicated by a raphe continued along the under side of the penis and into the perineum. Beneath the integument is a red- dish tissue, called the dartos, composed of non-striated muscular fibres, and in which resides the contractile power belonging to the scrotum. The testicle lies within a serous membrane, derived from the peritoneum of the abdomen, which was pushed before it in its descent during foetal life; the connection between the portion of membrane enveloping the testicle and the peritoneum of the general cavity of the abdomen being obliterated, it forms a separate shut sac by itself, called the tunica vaginalis. In the adult, as well as in infants, there is constantly found, at the point where the testicle and epididymis become continuous, a small cellulo-fibrous and fatty body, the size of a pea ; covered with serous membrane, and evidently analagous to the appendi- 200 ANATOMY OF THE ABDOMEN, ETC. ces of other serous membranes, especially of the peritoneum; it is sometimes pediculated, and at others consists merely of a little membranous fold. This has been called the appendix of the tes- ticle. The testicle should be examined by following out the vas deferens till it is lost in the epididymis, and then tracing that body to its connection with the main part of the gland, removing with the scissors all the cellular tissue that surrounds it. The close adherence of the parts to each other makes the dissection a slow one. The Testes are oval glands, suspended in the scrotum by the spermatic cord; the left one is usually larger and placed lower than the right. Along the posterior side, close to that part at which the tunica vaginalis is reflected to the testicle, is a long narrow body, called the epididymis, the lower part of which is continuous with the vas deferens, which turns and is reflected upwards beside the epididymis, being tortuous and wavy at first, but subsequently becoming straight as it unites with the other elements of the spermatic cord. The dissection will show that besides the serous coat, the testicle has also a fibrous coat of a pearly aspect, called the tunica albuginea ; this not only preserves the shape of the gland but sends processes into its interior for its further support; one of these, larger than the rest, lies along the posterior aspect of the gland, and is called the mediastinum testis. The substance of the testicle is a pulpy mass, made up of lobules composed of the convoluted tubuli seminiferi, which, if seized by the forceps, may be drawn out in long threads. The lobules all converge towards the mediastinum, where their tubuli unite and becoming larger, continue to the upper end of the tes- tis, and finally terminate in the vas deferens. Sometimes there is an offset from the vas deferens or lower part of the epididy- mis, consisting of a prolongation of the tubuli, extending up the cord and terminating in a blind extremity, called the vasculum aberrans of Holier. The vas deferens occupies the posterior part of the spermatic cord, and is easily distinguishable by its cord-like feel. Its course has been already'described (p. 196). The spermatic cord, besides the vas deferens, is made up of the spermatic artery and veins, and numerous lymphatics, which ter- minate in the lumbar glands. The spermatic veins are extremely FEMALE ORUANS OF - GENERATION. 201 subject to enlargement, and frequently seem to make up a very considerable portion of the cord; they may oftentimes be made out without injecting, commencing at the lower part of the testi- cle in numerous small, tortuous branches, which, surrounding the vas deferens, are called the rele pampiniforme ; these, gradually enlarging, terminate in the single trunk of the spermatic vein at, or near, the external abdominal ring. The cord also contains the spermatic plexus of nerves, which, coming from the aortic and renal plexuses, accompanies the spermatic artery. The genital branch of the genito-crural nerve and the scrotal branch of the musculo-cutaneous nerve (p. 182), are elements of the cord; and the creiuaster muscle (p. 149), variably developed, the spermatic fascia and the fibro-cellular tissue, the remains of the tube of peritoneum, once connecting the abdominal cavity, also make up a large portion of its bulk. FEMALE ORGANS OF GENERATION. The relations of the organs peculiar to the female sex have been already studied ; it remains to examine, in detail, the uterus and its appendages, including the external organs. The latter will be examined first. The prominence of the pubes, covered with a development of hair, is called the mons Veneris. Extending downwards from this are the labia majora, composed of two folds of integument, meet- ing above and below, filled with fat and cellular tissue, and lined internally with mucous membrane; the round ligament of the uterus terminates in these. Inferiorly, upon separation, a trans- verse fold will be seen stretching across between them, called the fourchette; in women who have borne children, this is usually destroyed. Superiorly will'be noticed the clitoris, a small pro- jecting body, analogous to the penis of the male, composed of two corpora cavernosa, attached on each side to the ramus of the ischium, and receiving the insertions of the erector clitoridis mus- cle. The clitoris is composed, like the penis, of erectile tissue, and is surmounted by a glans surrounded by a prepuce. From this prepuce, a longitudinal fold of mucous membrane descends 202 ANATOMY OF VTHE ABDOMEN, ETC. on each side, and becomes blended with the labia majora ; these folds are called the nympha, or labia minora. Between these, and just above the aperture of the vagina, is the orifice of the urethra, surrounded by an elevated margin. The urethra is about an inch and a half in length, and lies in the upper wall of the vagina, from which it cannot be separated ; it is very elastic, and capable of great distension. The orifice of the vagina is transversely elliptical; in the virgin it is sometimes partly closed by a circular fold of mucous membrane, called the hymen ; after childbirth this is destroyed, but its former presence is indicated by small elevated excrescences, called caruncula myrtiformes. Just anterior to the hymen may be found the orifices of two ducts, one on each side, often made apparent from being distended with sebaceous matter; by laying these open, they may be traced to a round body, the size of a large pea, called the gland of Bar- tholinus. The parts just described, are supplied by branches of the inter- nal pudic artery, and by offsets from the lumbar and sacral plex- uses of nerves. The bladder may now be dissected from the uterus, and the vagina laid open with the scissors along its superior surface. The vagina occupies a position corresponding to the axis of the outlet of the pelvis, and reaches from the cervix of the uterus, which projects into it, to the external opening of the vulva ; it is placed between the bladder and the rectum, and at its sides is embraced by the levatores ani muscles. Its orifice is surrounded by a sphincter muscle (p. 187), and its upper extremity is dilated; its internal surface is lined with mucous membrane, thrown into rugae, more marked near the entrance than higher up; these meet in a raphe that extends along the centre of both the ante- rior and posterior walls; the two raphes being called the columns of the vagina. Beneath the mucous membrane is a layer of erec- tile tissue similar to the dartos, and external to this a layer of cellular tissue ; the upper part of the posterior wall of the vagina is covered by the peritoneum of the recto-uterine fold. The Uterus, with the exception of its mouth and neck, is cov- ered with peritoneum, which spreads out on both sides into what is called the broad ligament, stretching across the pelvis, as al- ready seen, and forming a sort of septum between the bladder and FEMALE ORGANS OF GENERATION. 203 rectum. It is pyriform in shape, convex posteriorly, and flattened anteriorly, and is divided into a fundus, body, cervix, and os. The uterus may be laid open with the scissors, introduced at the os, making a longitudinal incision to be afterwards crossed by a transverse one at the fundus. The substance of the uterus'is composed of muscular fibres. In its natural state, the muscular portion is seen as a firm, compact, fibrous tissue ; in the impregnated condition, this becomes hyper- trophied and vastly more apparent. The orifices of divided veins will be seen on the face of the section; these, in the pregnant uterus, are called the sinuses. The cavity of the uterus is lined with mucous membrane continuous with that of the vagina; it is triangular in shape, and about the size of an almond; the base of the triangle corresponds to the fundus of the organ, the fundus being the broad portion surmounting the body, or central part. The cavity is constricted at the union of the body with the cervix, the cervix being the portion between this constriction and the os. The point of constriction between the cervix and body is some- times called the os uteri internum. The canal of the cervix is slightly dilated, and the oblique folds of the mucous membrane, in this part, have received the name of arbor vita uteri. The os uteri, before parturition, consists simply of a rounded orifice with thick lips ; after childbirth it becomes a transverse fissure, the posterior lip of which is the longest. The uterus is supplied with blood from the uterine and ovarian arteries. The uterine veins are large and numerous, and form plexuses upon each side of the organ ; its nerves are derived from the hypogastric and ovarian plexuses, and from branches of the third and fourth sacral nerves. The appendages of the uterus are the broad ligaments, the round ligaments, the Fallopian tubes, and the ovaries. The broad ligaments, consisting simply of the two folds covering the anterior and posterior uterine surfaces, and those reflected upon the walls of the pelvis, have been already referred to. The round ligaments are round cords of fibrous tissue attached to the sides of the fundus uteri, and which, passing upwards and outwards, to the internal inguinal ring and through the inguinal canal, like the spermatic cord in the male, are lost in the mons Veneris and labia majora. 204 ANATOMY OF THE ABDOMEN, ETC. The Fallopian tubes, about four inches in length, are connected by one end with each side of the fundus of the uterus ; the other end is loose in the cavity of the pelvis. Their canal is very mi- nute, but traceable with a fine probe to the opening at the angles of the cavity of the uterus, with the mucous membrane of which their own becomes continuous. The outer termination of the tube is free in the peritoneal cavity ; it is dilated and surrounded by a circular, fringe-like fold, called corpus fimbriatum, or morsus dia- boli. It will be noticed that there is thus a communication be- tween the cavity of the uterus and that of the peritoneum, form- ing a single exception to the general rule that serous membranes are shut sacs. The Ovaries are two white, oblong bodies, with either a smooth or a scarred surface, bulging from the broad ligaments on their posterior aspect, and connected with them by their anterior margins. They are attached to the uterus by their inner extrem- ity, through the medium of rounded cords called the ligaments of the ovary. The ovary consists of a fibrous structure containing small vesicles, called Graafian, and the peritoneum surrounds the whole organ, except at its attached border. Their dimensions are very variable, but may be stated, in a general way, as an inch and a half, by three quarters of an inch in their diameters, and half an inch in thickness. The ovaries are supplied by the ovarian arteries, which anas- tomose with the uterine. The ovarian plexus of nerves, derived from the aortic, accompanies the ovarian artery, and the uterine nerves are also, in part, distributed to them. It is not always easy for the student to tell which is the front and which the back of the uterus; the ovaries, when present, will tell him ; they being always placed on the posterior aspect of the broad ligament; in their absence, he must remember that the uterus is convex posteriorly, and flat anteriorly. ANTERIOR FEMORAL REGION. 205 DISSECTION VIII. ANTERIOR FEMORAL REGION. In studying the anatomy of femoral hernia, the superficial structures of the an- terior femoral region have, in part, been examined. The incision of the skin may now be carried down the front of the thigh to the knee, and the integument re- flected; several cutaneous nerves will be exposed by this process. The Cutaneous Nerves are branches of the external cuta- neous, genito-crural and crural nerves, all being branches of the lumbar plexus. The external cutaneous pierces the deep fascia just below the anterior superior spinous process of the ilium, and is distributed to the integument of the anterior part of the gluteal region and the outside of the thigh. The crural branch of the genito-crural nerve is small in size, and emerging from the sheath of the femoral artery, is distributed to the anterior aspect of the thigh. The crural nerve, appearing just below Poupart's liga- ment from between the psoas and iliacus muscles, divides into a large number of branches, cutaneous and muscular, distributed to the integument and anterior muscles of the thigh. The internal saphenous vein, especially if distended with blood, will be easily traced, in its superficial course upwards, to the saphe- nous opening. This vessel affords the best opportunity to exam- ine the venous valves; they are formed from the internal lining membrane, and are usually in pairs, and of a semi-lunar shape; their situation is indicated externally by the dilatation of the vessel in front of them. Upon the outside of the thigh the deep fascia, or fascia lata, will be found to become more aponeurotic, and, at its upper part, to divide into two layers, between which lies the tensor vaginae femoris. The Tensor Vaginae Femoris is a short and thick muscle, arising from the anterior superior spinous process, and a portion of the crest of the ilium ; it is inserted into the fascia lata between its two layers, at a point five or six inches below that of its origin. The fascia lata may be removed as far as the anterior border of the tensor vaginae muscle, but it should not be divided transversely until the vastus extemus is dis- sected. ' The removal of that part in front of the thigh exposes the sartorius and rectus muscles. In dissecting the sartorius it will be found advantageous to re- move its anterior sheath without disturbing the posterior adhesions which keep the muscle in place; when this is accomplished it may be dissected posteriorly, but 206 ANATOMY OF THE LOWER EXTREMITY. it is so long a muscle that it is impossible to keep it tense, and therefore to dissect it neatly. The Sartorius Muscle arises from the anterior superior spinous process of the ilium, and crosses the thigh obliquely to the inside of the knee, where it forms a thin, flat tendon which is inserted into the inner tuberosity of the tibia by an aponeurotic expansion, which loses itself in the fibrous tissues surrounding the knee joint. In dissecting the origins of the three following muscles, they must be free from all tension; but in preparing their bellies and insertions they should be made tense, and this will be accomplished by bending the knee upon the thigh. The length and flaccidity of the sartorius permit its being drawn to one side, so as not to interfere with the dissection of the parts beneath it. The second hetid of the rectus is not easily seen, as it is very short; by lifting the muscle upwards and inwards it may be isolated from the surrounding parts, and brought into view. The Rectus Femoris Muscle lies upon the front of the femur, forming a beautiful belly, the fibres of which radiate from a central longitudinal line in a bipenniform manner. It arises by two tendinous heads, one from the anterior inferior spinous process of the ilium, just below the origin of the sartorius ; the other from the upper surface of the acetabulum; it is inserted by a broad flat tendon into the upper border of the patella. The Vastus Externus Muscle is partly covered in by the fascia lata into which the tensor vaginae femoris is inserted; it forms the bulk of the outer, fleshy part of the thigh ; it arises from the base of the trochanter major, and from the whole length of the linea aspera, and is inserted into the outer side of the patella, form- ing a common aponeurotic tendon with the rectus muscle. The Vastus Internus Muscle forms the bulk of the fleshy portion of the lower part of the thigh at its inner side, giving the limb its characteristic outline; it arises from the anterior and lateral surfaces of the femur, and from the whole length of the linea aspera; its lower end terminates in an aponeurosis, which, blending with that of the rectus, is inserted into the inner border of the patella. The upper part of the muscle is hidden beneath the rectus and sartorius muscles; the adductor muscles are in- separably connected with that portion attached to the linea aspera. The portion lying beneath the rectus muscle, the fibres of which run longitudinally from the inter-trochanteric line to the patella, is sometimes described as a separate muscle, called the cruraus. ANTERIOR FEMORAL REGION. 207 The sub-cruraus muscle is a small bundle of fibres beneath the cruraMis, arising from the front part of the femur, and inserted into the synovial sac of the knee-joint. These three muscles are sometimes looked upon and described as one muscle with three heads; the patella is then considered as a sesamoid bone, and the ligamentum patellae, inserted into the tubercle of the tibia, as the real tendon of insertion to the three muscles combined under the name of triceps extensor cruris. If the cruraeus is included with the other three muscles, the term quadriceps is used. These muscles are all supplied by branches of the crural nerve, and the femoral artery sends off irregular muscular twigs, which penetrate them on their under surface. The muscles upon the inner and upper part of the thigh almost invariably be- come dried and defaced from the delay occasioned by the examination of other parts after their exposure in the dissection of femoral hernia; if they have been kept properly moist, they will however still be found in tolerable condition. If the subject be entire, the knees should be bent and the soles of the two feet placed in contact with the heels pushed up and so approximated to the pelvis that they will retain their position. If the limb is separated from the trunk, the ilium must be fixed by blocks, and the muscles of the inside of the thigh rendered as tense as circumstances will permit. The muscles of the inner side of the thigh are the three ad- ductors, (longus, brevis, and magnus,) with the gracilis and pecti- neus. The gracilis is the longest and most internal; superficial to the others are the pectineus and the adductor longus, and be- neath these the adductors brevis and magnus. The Gracilis Muscle arises by a thin, flat, and broad tendon from the side of the symphysis of the pubes and from the ramus of the pubes and ischium; it forms a long flattened belly, which, passing down on the inside of the thigh, terminates in'a tendon, rounded at first, but becoming flattened, and is inserted into the head of the tibia beneath the expanded insertion of the sartorius. The Adductor Longus consists of a large fleshy belly arising by a round, tendinous origin from the front of the os pubis, and inserted into the middle third of the linea aspera by an aponeuro- sis which is partially confounded with that of the adductor mag- nus. The dissection of this muscle at its upper part will expose the profunda artery, and at its insertion the femoral artery will be seen in close relation to it. Between this muscle and the femur lies the Pectineus, aris- ing by a broad and flat muscular origin from the ilio-pectineal line, 208 ANATOMY OF THE LOWER EXTREMITY. and inserted into the ridge leading from the lesser trochanter to the linea aspera. It is not easy to find the line of separation between this muscle and the conjoined tendon of the psoas and iliacus, the insertion of which into the lesser trochanter may now be seen (p. 183). The Triangle of Scarpa is the triangular depression in the upper part of the thigh, the base of which is formed by Poupart's ligament, the outer side by the conjoined tendon of the psoas and iliacus, and the sartorius, and the inner side by the pectineus and adductor longus. The femoral artery runs through the centre of this hollow with the femoral vein internal to it; half an inch external to the artery is the crural nerve, at first deep-seated be- tween the psoas and iliacus, afterwards becoming more superficial. The Femoral Artery extends from Poupart's ligament to the point at which it perforates the adductor magnus muscle ; it is covered in by a strong sheath common to it and the vein, and oc- cupies the depression existing between the adductor muscles on the inside of the thigh and those which cover the femur upon the out- side ; it lies upon the psoas, pectineus, and adductor longus muscles, and the femoral vein, except at the upper part, where it is upon its inner side, lies almost directly behind it; it is accompanied by the long saphenous nerve within the sheath, and by the short saphe- nous nerve outside. It disappears through an aperture in the tendon of the adductor magnus muscle at the union of the mid- dle and lower third of the thigh, and its course from the com- mencement to this point is indicated, when the limb is rotated outwards, by a line drawn from the centre of Poupart's ligament to the most prominent part of the internal condyle ; the sartorius muscle, usually called the satellite of this artery, crosses the thigh at such constantly varying angles, that its relation to it is by no means constant. The artery may sometimes be found split into two trunks below the origin of the profunda; these, however, always unite before the vessel perforates the adductor magnus. The long and short saphenous branches of the crural nerve will be observed accompanying the femoral artery, the former within its sheath and the latter upon its outside; at the opening in the adductor muscle, the long saphenous becomes superficial, and de- scending the inner side of the leg with the saphenous vein, is distributed to the integument as far down as the inner side of the foot. The short saphenous nerve is distributed to the muscles ANTERIOR FEMORAL REGION. 209 and integument of the inner side of the thigh, and anastomoses with filaments of the long saphenous and obturator nerves. The superficial branches given off by the femoral artery have been already dissected and described, at p. 178, in connection with the anatomy of femoral hernia. At a variable distance, viz : from one half to two inches below Poupart's ligament, it gives off posteriorly a large branch, nearly equal in size to the femoral itself, and called the profunda artery. This, passing backwards behind the adductor longus, breaks into branches which perforate the muscles, and are distributed to the parts on the back of the thigh. The dissection of the profunda is with difficulty accomplished, without destroy- ing parts yet to be dissected, owing to the number of its branches, the confined limits of the space they occupy, and the depth to which they penetrate. The scis- sors will be found useful at this time, and, by the aid of hooks and a judicious posi- tion of the limb, the soft fat and cellular tissue surrounding the arteries may be removed, and the branches, if not too much meddled with by the forceps, neatly displayed. The profunda gives off an external and an internal circumflex artery; one or both of these sometimes arise directly from the femoral. The external circumflex is the larger of the two; it passes outwards be- neath the rectus muscle and divides into three branches or sets of branches viz: ascending, to inosculate with the gluteal on the dorsum of the ilium near its crest; middle, which curve around the femur just beneath the greater trochanter, to inosculate with the gluteal and internal circumflex; and descending, which are distributed to the muscles of the outside of the thigh. The internal circumflex passes beneath the heads of the adductor mus- cles on the inside of the thigh, and is only to be farther traced by their division; it supplies these muscles, and inosculates with the external cir- cumflex and the ischiatic The terminal branches of the profunda are called the perforating arte- ries, because they pass through foramina in the adductor tendons to reach the back part of the thigh. They are.usually three in number; they anastomose freely with each other, with the ischiatic and internal circum- flex above, and the articular branches of the popliteal artery iuferiorly. One of these arteries gives the nutrient branch to the femur. These branches of the femoral artery are all accompanied by veins which unite to form the profunda vein, which enters the femoral vein an inch or more below Poupart's ligament. The femoral artery furnishes muscular branches to the muscles 14 210 ANATOMY OF THE LOWER EXTREMITY. contiguous to it, and as it is about to perforate the adductor magnus, gives off a branch called the anastomotica magna. The anastomotica magna is not usually of large size, nor always con- stant in its point of origin, not unfrequently arising from the popliteal; it is accompanied by the long saphenous nerve, and descending to the inner condyle, inosculates with the superior internal articular branch of the popliteal. In very finely injected subjects, numerous anastomoses may be traced between this artery and other branches distributed to the neigh- borhood of the knee-joint. The pectineus and adductor longus may now be divided in the middle, and their ends reflected. The arteries should be preserved so far as possible. In removing these muscles, the obturator nerve and its branches should be sought for; emerging from the pelvis (p. 183) it is distributed to the muscles of the inner side of the thigh, and a long branch passing behind the pectineus, descends to the knee, where it joins with branches of the long saphenous nerve. Small branches of the obturator artery will also be found at the upper part of these muscles. The Adductor Brevis l;es immediately beneath the two muscles just divided ; arising by a narrow origin from the exter- nal surface and ramus of the os pubis, and passing very obliquely inwards, it is inserted by a broad tendon behind the pectineus into the upper part of the linea aspera. The Adductor Magnus, the deepest of the three adductors, forms the bulk of the upper part of the thigh, and separates the muscles of the anterior and posterior femoral regions; superiorly it lies beneath the adductor brevis, which must consequently be removed. It arises from the ramus of the pubis and ischium, and from the tuberosity of the ischium, and is inserted into the inter-trochanteric line, and the whole length of the linea aspera, as far as the inner condyle, where it terminates in a small, rounded tendon. At its lower part it becomes confounded with the adductor longus and the vastus internus muscles. At its upper part it is pierced by the perforating arteries, and lower down it has a large, oval, and tendinous opening, converted into a canal by the vastus internus, through which pass the femoral vessels. By detaching the origin of the adductor magnus, the obturator externus will be exposed. The Obturator Extern us Muscle arises from the ramus of GLUTEAL REGION. 211 the pubes and ischium, and from a part of the surface of the obtu- rator membrane; it forms a triangular belly, and its fibres con- verge to a rounded tendon, which is inserted into the digital fossa of the great trochanter. The obturator artery (p. 190), after emerging from the pelvis, forms a circle around the membrane beneath this muscle, and sends an articular twig, through the notch of the acetabulum, to the head of the femur, which it reaches by means of the round ligament. DISSECTION IX. GLUTEAL REGION. The subject should be turned over, and a high block placed beneath the thighs, in such a way that the pelvis may hang over its edge, and yet remain fixed firmly enough for dissection; the thigh should be rotated inwards, and the foot should lie upon its outer side. An incision is to be made obliquely outwards from the upper part of the sacrum, a hand's breadth below the greater trochanter; this should penetrate to the muscle, and the flaps be reflected by dissecting in the di- rection of its fibres. The skin is thick and tough, and there is a deep layer of fat beneath it, which will probably be found more or less infiltrated with the fluids which have gradually gravitated into the part whilst dependent. The gluteus maximus, which is the first muscle exposed, is composed of coarse bundles of fibres, between which penetrate prolongations from its sheath. It is one of the most difficult muscles in the body to dissect neatly, though in a favorable sub- ject, and when well dissected, few present a more showy appear- ance. The Gluteus Maximus Muscle arises from the posterior fifth of the crest of the ilium, and the bone beneath, the lateral tubercles of the sacrum, the sacro-iliac and sacro-ischiatic liga- ments, and from the side of the coccyx ; its upper half is inserted into a thick, flat tendon, continuous with the fascia lata of the thigh; the lower portion is inserted into the rough line on the femur, leading from the trochanter major to the linea aspera. Beneath this broad tendon is a large synovial bursa. The upper border of this muscle is closely connected with the gluteus me- dius, by a prolongation of the fascia lata; its lower border forms 212 ANATOMY OF THE LOWER EXTREMITY. the fold of the nates, a»d overlaps the origins of the muscles of the back of the thigh. This muscle is to be divided transversely, and its two ends are to be reflected; this will expose the gluteus medius. In dividing the gluteus maximus, a number of arterial twigs, distributed to the muscle, will be cut across; they are muscular branches of the gluteal and ischiatic. arteries; a few ascending twigs from the external circumflex will also be seen. The Lesser Sciatic Nerve, coming from the sacral plexus, emerges with the ischiatic artery at the sacro-sciatic foramen. Its branches supply the integument and the gluteus maximus, which it penetrates at its lower border; some of its branches de- scend and are distributed upon the posterior aspect of the thigh; one of these, larger than the others, is called the middle posterior cutaneous. The Gluteus Medius Muscle, partially covered by the gluteus maximus, and elsewhere by a dense aponeurosis, which cannot be dissected from the muscular tissue beneath, arises from the anterior four fifths of the crest of the ilium at its anterior bor-' der, being closely connected with the tensor vaginae femoris; its fibres converge, to be inserted into the external surface of the trochanter major. The gluteal artery emerges at its posterior border, and a large branch ramifies upon this muscle, between it and the gluteus maximus. This muscle may now be removed, by dividing it an inch above its insertion, and reflecting its muscular belly. A confused mass of cellular tissue, arteries, nerves, and muscles, remain, which is to be patiently cleared up, by gradually removing the areolar substance with the scissors and forceps, following out the arteries and nerves; the tracing of them should be commenced at the point at which they emerge from the pelvis. The gluteal artery emerges between the gluteus medius and pyriformis muscles, and is, as we have seen (p. 191), a branch of the internal iliac, the terminal one of its posterior division; it breaks up into branches as soon as it emerges from the pelvis. The superficial branch goes to the gluteus maximus; the deep superior passes upwards and forwards to the anterior superior spinous process of the ilium, between the gluteus medius and minimus, and inosculates with the circumflexa ilii and external circumflex, and the deep inferior branch ramifies upon the glu- teus minimus, in the neighborhood of the trochanter and capsule of the hip-joint. GLUTEAL REGION. 213 The gluteal nerve, coming from the sacral plexus, emerges with the gluteal artery, and divides into two branches; one, passing upwards towards the crest of the ilium, and supplying the gluteus medius and minimus, and the other, passing forwards, also sends branches to these muscles, and terminates in the ten- sor vaginae femoris. The ischiatic artery, one of the terminal branches of the ante- rior division of the internal iliac, emerges below the pyriformis muscle, and passes downwards between the trochanter and the tuberosity of the ischium, supplying muscular branches to the gluteus maximus and posterior muscles of the thigh; it also sends a branch to the great sciatic nerve, named comes nervi ischiatici, which accompanies it to the popliteal space. The Great Sciatic Nerve is the continuation of the sacral plexus. It emerges below the pyriformis muscle as a broad, flat cord, three fourths of an inch in width ; it descends between the trochanter and tuberosity of the ischium, and will be further seen in the dissection of the posterior region of the thigh. It supplies the heads of the posterior muscles of the thigh, and small branches ramify on the capsule of the hip joint. Not unfrequently it is split into two trunks, one of which passes through the pyriformis; sometimes the whole nerve perforates that muscle. The internal pudic artery emerges below the pyriformis mus- cle, in front of the ischiatic artery, at the great sacro-sciatic foramen, passes under the greater sacro-ischiatic ligament, and ascends along the ramus of the ischium; it is accompanied by the internal pudic nerve ; its branches and distribution have already been described (p. 185). In dissecting these arteries, the following muscles will have been exposed. The Gluteus Minimus Muscle arises, fan-shaped, from the ilium, between the acetabulum and the superior curved line, and is inserted into the summit and inside of the great trochan- ter ; anteriorly this muscle is confounded with the gluteus me- dius. The Pyriformis Muscle, arising from the sacrum has al- ready been seen within the pelvis (p. 194); the part external to the pelvis is now seen tapering to its insertion and separated from the gluteus minimus by the gluteal artery. It arises from 214 ANATOMY OF THE LOWER EXTREMITY. the concave surface of the sacrum, between the first and fourth anterior sacral foramina, from the greater sacro-ischiatic ligament, and from a portion of the ilium; forming a thick flattened belly, it passes out at the great sacro-ischiatic notch, tapers to a rounded tendon, blending with that of the gluteus minimus, and is inserted into the digital fossa of the great trochanter. Some little difficulty Is often experienced by the student in determining the three next muscles. A bundle of muscular fibres presents itself just below the pyri- formis. and crossed by the great sciatic nerve; it is composed of the tendon of the internal obturator surrounded by its two dependent muscles, the gemelli; if this bundle of fibres be carefully separated longitudinally, the glistening tendon of the obturator will be exposed, and the two gemelli may be distinctly separated on one side and the other, though not isolated from the obturator tendon. The Obturator Internus Muscle has been partly seen in another dissection (p. 193); it arises within the pelvis from the margin of the bone which surrounds the obturator foramen, and from the membrane which stretches across it; it passes over the lesser sacro-ischiatic notch, which acts as a pulley on which its tendon plays in the change of direction which it assumes in reach- ing its insertion. The belly of the muscle is broad and flat, and tapering to a rounded tendon, embraced by the gemelli, is inserted into the digital fossa of the great trochanter. By dividing the muscle, it will be seen that the sciatic notch is covered with car- tilage and provided with a synovial bursa. The Gemellus Superior arises from the spine of the ischium; the Gemellus Inferior from the upper and posterior part of the tuberosity of the ischium. The superior is usually the smaller of the two, and they embrace and either wholly or partially con- ceal the tendon of the obturator, into which some of their fibres are inserted, whilst the rest are inserted with that tendon into the digital fossa of the greater trochanter. The gemellus supe- rior is sometimes absent. The Quadratus Femoris Muscle lies next below the gemel- lus inferior; it is a flat and quadrangular muscle arisiuo- from the external border of the tuberosity of the ischium, and inserted into the linea quadrati on the posterior and outer part of the greater trochanter. This muscle is tendinous at its insertion, and its lower border is in relation with the adductor magnus ; it is crossed by the sciatic nerve, and the internal circumflex artery emerges at its upper border. Just above this muscle will be seen the POSTERIOR FEMORAL REGION. 215 tendon and part of the belly of the obturator externus, going to be inserted into the digital fossa, DISSECTION X. POSTERIOR FEMORAL REGION. An incision is to be carried down the back of the thigh, to a short distance below the fold of the knee-joint, and the integument reflected. Upon the fascia lata thus exposed will be found a number of cutaneous nerves, on the inside derived from the short saph- enous or obturator, on the outside from the external cutane- ous, and in the middle from the middle posterior cutaneous. Towards the lower part of the thigh, the external saphenous vein may be seen penetrating the popliteal space to join the pop- liteal vein. The fascia lata is to be removed and the muscles are to be dissected. The sciatic nerve and its divisions are to be particularly respected. The posterior femoral muscles will be found supplied with arteries from the circumflex and perforating branches of the profunda. The Biceps Muscle is the most external of these, and, in common with the two muscles next described, is covered in at its upper part by the gluteus maximus. It arises from the tuberosity of the ischium by a tendon only artificially separable from the other muscles arising at that point, and also from the femur by a second head attached to the linea aspera; these two heads unite to be inserted by a round tendon into the head of the fibula and outer tuberosity of the tibia. This tendon forms the outer ham- string.* The Semi-tendinosus Muscle lies upon the inner side of the posterior femoral region. At its origin from the tuberosity of the ischium, and for some distance below it, it is not easily sepa- rable from the biceps; it forms a comparatively short and stout * The student of this locality can assist his memory to retain the fact that the biceps forms the outer hamstring by the first two letters in the word Boston. (B. 0. biceps, outer.) 216 ANATOMY OF THE LOWER EXTREMITY. belly, terminating in a long tendon, which is inserted into the inner surface of the tibia below the tendon of the gracilis, both of these tendons being covered in by the expanded insertion of the sartorius. The Semimembranosus Muscle lies beneath the two pre- ceding muscles, and derives its name from the membraniform tendon which characterizes its origin. It arises from the tuber- osity of the ischium in common with the biceps and semi-tendino- sus, and is inserted by a tendon which has three different points of attachment, viz: an internal one to the inner tuberosity of the tibia; a middle one, which is continuous with the fascia, cover- ing the popliteus muscle, and a posterior one which expands upon the posterior surface of the knee-joint and is attached to the outer condyle of the femur, constituting what is called the liga- mentum posticum Winslowii. The tendons of the semi-mem- branosus and semi-tendinosus form the inner ham-string, and with that of the gracilis, from a fancied resemblance, have received the name of the pes anserinus. The Sciatic Nerve, surrounded by a considerable amount of fat and areolar tissue, will have been traced in the foregoing dis- section. At the upper part of the thigh, it is comparatively super- ficial, there being no muscle between it and the integument; it then passes underneath the long head of the biceps, and down upon the outer side of the median line of the thigh to the popliteal space, giving off, in its course, branches to the muscles of the posterior femoral region, and a single articular branch to the knee-joint. Towards the lower part of the thigh, it divides into the popliteal and peroneal branches ; sometimes this division takes place higher up, even before emerging from the pelvis; in which case, as has been seen, one of the branches perforates the pyriformis muscle. popliteal space. The Popliteal Space is the interval between the biceps and semi-tendinosus and semi-membranosus above, and the separated heads of the gastrocnemius below; its base, or floor, being the flat surface of the femur above the condyles; the fascia lata and integument cover it superficially, and it is traversed by the popli- teal artery and vein, and the sciatic nerve with its branches. POPLITEAL SPACE. 217 The branches of the sciatic nerve, being the most superficial, will be examined first. The peroneal division of the sciatic is smaller in size than the popli- teal ; it accompanies the tendon of the biceps tq the head of the fibula, where it curves around that bone, passing between it and the peroneus longus muscle, dividing, as it disappears, into the anterior tibial and mus- culo-cutaneous. The peroneal nerve, before disappearing, besides giving off' a few small cutaneous, muscular, and articular branches, furnishes an important superficial branch, the communicans peronei; this passes down upon the outer side of the calf of the leg to about its middle, where it is joined by a branch from the popliteal, called the communicans poplitei, and the two, uniting, constitute the external saphenous nerve. The popliteal nerve lies superficial to the artery, and, at the lower bor- der of the space, becomes the posterior tibial nerve; whilst in the space, it gives off muscular branches to the heads of the gastrocnemius, an ar- ticular branch to the interior of the knee-joint, and a superficial branch, called the communicans poplitei; this is larger than the communicans peronei, with which, after passing between the two heads of the gastroc- nemius, it unites half-way down the leg; their union constitutes the external saphenous nerve. The Popliteal Vein lies in front of the artery, and receives the external saphenous vein, which, from its superficial course, penetrates here to terminate in the popliteal. The Popliteal Artery lies deeply imbedded in the popli- teal space ; it is the continuation of the femoral artery; com- mencing at the point where that vessel emerges from the adductor magnus, it tenninates at the lower border of the popliteus muscle, by dividing into the anterior and posterior tibial arteries; this division sometimes takes place at a point higher up. The popliteal gives off four articular branches, viz : a superior and inferior, external articular, and a superior and inferior, inter- nal articular. These wind around the knee-joint to its front, supplying the lower part of the femur and the heads of the tibia and fibula and the joint itself; they anastomose very freely with each other, with the anastomotica magna, and the recurrent branch of the anterior tibial artery. The inferior articular arte- ries pass beneath the lateral ligaments of the knee-joint, and the superior articular beneath the tendon of the biceps, on the out- side and that of the adductor magnus on the inside. Two large muscular branches, called the sural, pass downwards, to supply each head of the gastrocnemius muscle, and the azygos articular. 218 ANATOMY OF THE LOWER EXTREMITY. a small branch, almost always broken or destroyed in removing the fat from the popliteal space, arises from the posterior aspect of the artery, and penetrates the ligamentum posticum, to supply the internal structures of the knee-joint. DISSECTION XL FRONT OF THE LEG AND DORSUM OF THE FOOT. The dissection now reverts to the front of the limb, and is continued by making an incision from the knee downwards and along the dorsum of the foot. The integument alone should be reflected. The front of the leg will be found encased by a strong, glisten- ing fascia, continuous with the fascia lata of the thigh ; upon this will be found the internal saphenous vein, and, at the junction of the middle and lower third, the continuation of the musculo- cutaneous branch of the peroneal nerve will be seen emerging through an aperture in the fascia. The internal saphenous vein commences at the great toe, and passes up along the inner side of the leg, and behind the inner condyle, to the saphenous opening, where it terminates in the femoral vein. The musculocutaneous nerve, after its division from the pero- neal at the head of the fibula, passes downwards between the muscles of the leg to emerge through a distinct foramen in the fascia; it then divides into two branches, called the peroneal cuta- neous ; these pass down superficially, and at the toes divide again into branches, distributed to their sides. On the dorsum of the foot, the termination of the anterior tibial nerve will be found, accompanying the dorsalis pedis artery in the first interosseous space; this nerve supplies the great toe, and the outer side of the next. Along the outer border of the foot will be found the termina- tioif of the external saphenous nerve, which supplies the tittle toe, and sometimes the outer side of the next. The fascia of the leg, extending across from the anterior sur- face of the tibia to the fibula, is extremely dense, and, at the upper part of the leg, binds down and is closely adherent to the muscles beneath, some of their fibres originating from it. At the ankle, FRONT OF THE LEG AND DORSUM OF THE FOOT. 219 it forms the anterior annular ligament; this is a thickened portion, crossing from the external to the internal malleolus, and the limits of which are imperfectly defined; it contains sheaths for the ten- dons of the muscles, which pass down from the leg to the dorsum of the foot. The fascia of the leg should be removed, by detaching it from below upwards; where it becomes blended with the bellies of the muscles, it should be left in con- nection with them. The annular ligament is not to be removed. The muscles of this region should be separated from each other, by following them up from their tendons. The Tibialis Anticus Muscle lies along the side of the tibia, arising from the upper two thirds of its inirer surface and from the interosseous membrane; its tendon passes through a separate sheath in the annular ligament, and is inserted into the side of the internal cuneiform bone and the head of the first me- tatarsal bone. The Extensor Proprius Pollicis is a thin muscle, covered in by the tibialis anticus on one side and the extensor longus digi- torum on the other; it arises from the middle third of the fibula, and its tendon, which runs along the anterior border of the mus- cle, receiving the fibres in a penniform manner, passes through a separate sheath in the annular ligament, and is inserted into the base of the second phalanx of the great toe. The Extensor Longus Digitorum arises from the upper half of the fibula, from the head of the tibia and from the interos- seous membrane; its fibres are inserted in a penniform manner into three tendons which commence upon the anterior border of the muscle ; these pass through the annular ligament, and on the dor- sum of the foot the inner tendon divides into two, thus making four tendons destined to all the toes except the great toe. The tendons of the extensor brevis are inserted into the outer side of each of these tendons, with the exception of the one to the little toe, and the expanded tendon thus formed is inserted, as in the hand, by its division into three slips, the central one of which goes to the second phalanx, and the two lateral ones to the sides of the last phalanx. The Extensor Brevis Digitorum, covered in by the ten- dons of the extensor longus and peroneus tertius, lies upon the dorsum of the foot, and consists of a small, flat belly arising from the outside of the os calcis, from which emanate four tendons ; 220 ANATOMY OF THE LOWER EXTREMITY. the first crosses the dorsalis pedis artery, and is inserted into the first phalanx of the great toe, the other three terminate by blend- ing with the outer sides of the tendons of the extensor longus. The Peroneus Tertius Muscle is in reality a part of the extensor longus ; it arises from the lower third of the fibula as a thin layer of fibres, which terminate in a round tendon that passes under the annular ligament in the same sheath with the extensor longus, and is inserted into the base of the metatarsal bone of the fifth toe. It is not unfrequently wanting. Upon separating the tibialis anticus and the extensor longus, the anterior tibial artery will be found, lying deep in the upper part of the leg, but more superficial lower down. After its divis- ion from the popliteal, it pursues a short course posteriorly, to the space between the fibula and tibia, and becomes anterior by pass- ing through the interval left at the upper part of the interosseous membrane, upon which it descends in company with the anterior tibial nerve, and two large venae comites; in the upper part of its course it lies between the tibialis anticus and the extensor longus; lower down, between the tibialis anticus tendon and that of the extensor proprius pollicis, it passes u/idNer the annular ligament, and on the back of the foot becomes the dorsalis pedis artery. At its upper part it sends a recurrent branch upwards, which perfor- ates the head of the tibialis anticus and anastomoses with the inferior articular branches of the popliteal; in its course between the muscles it gives off numerous muscular twigs, and at the ankle- joint an external and internal malleolar branch; these supply the parts about the joint, anastomosing with calcanear branches of the posterior tibial and peroneal arteries. The anterior peroneal artery, coming from the back of the leg, passes through an aperture in the lower part of the interosseous membrane, and is distributed in front of the fibula to the dorsum and outer part of the foot, anastomosing with the malleolar branches of the anterior tibial. The anterior tibial nerve will be found passing obliquely under the belly of the extensor longus muscle, to accompany the ante- rior tibial artery lying on its outer side ; it emerges on the dorsum of the foot to be distributed as has been described. The musculo-cutaneous nerve lies between the extensor longus and the peronei muscles, and then pierces the fascia to be distrib- uted as has been described. BACK OF THE LEG. 221 The dorsalis pedis artery lies upon the outer side of the tendon of the extensor proprius pollicis; it is accompanied by the ante- rior tibial nerve; it distributes some branches to the tarsus, called tarsal, and then forms an arch over the base of the metatarsal bones; this arch gives off three interosseous branches which, at the commissures of the third, fourth, and fifth toes, divide into digital branches, to supply the sides of the toes. At each end of the interosseous space these arteries are joined by a perforating branch from the sole of the foot. At the base of the first interos- seous space, it penetrates to the sole of the foot, to unite, under the name of the communicating artery, with the termination of the plantar arch; before disappearing it gives off the dorsalis hallucis branch, which passes forwards and is distributed to the great toe and the inner side of the next. The Dorsal Interosseous Muscles arise by two heads from the sides of the heads of adjoining metatarsal bones; they are in- serted into the bases of the first phalanges of the toes and into the expansion of the extensor tendons; the first interosseous being inserted into the inside of the second toe, and the three others into the outsides of the second, third, and fourth toes. DISSECTION XII. BACK OF THE LEG. The dissection of the back of the leg is to be commenced by an incision from the popliteal space to the heel. The integument is to be reflected with care, as there are several superficial structures to be examined. The external saphenous vein, commencing on the outer border of the foot, ascends upon the outside of the tendo Achillis, over the belly of the gastrocnemius muscle and between its two heads, to the popliteal space, where it enters the popliteal vein. The external saphenous nerve, formed from the communicans peronei and poplitei, which unite at a variable distance down the leg, accompanies the external saphenous vein along the outer bor- der of the tendo Achillis; it curves around the external malleo- lus and is distributed to the little toe and outer border of the foot. 222 ANATOMY OF THE LOWER EXTREMITY. The muscles of the leg are arranged in two layers, superficial and deep ; the superficial layer constitutes the " calf of the leg." The Gastrocnemius Muscle, the first muscle of the superfi- cial layer, arises by two heads, of which the inner is the larger, from the surface of bone above each condyle of the femur; these heads converge and form the lower boundary of the popliteal space, being inside the tendons forming the ham-strings ; they are each supplied with an arterial branch, the sural, from the popli- teal artery. The large muscular belly of the gastrocnemius termi- nates in a brilliant aponeurosis which ends in a large round tendon, called the tendo Achillis, which is inserted into the poste- rior surface of the os calcis : this tendon, for some distance above its insertion, is common to this muscle and the soleus which lies beneath it. The small rounded tendon of the plantaris muscle, running along the inside of the tendo Achillis, to which it is more or less adherent, should be sought for and isolated, that it may not be cut across in dividing the gastrocnemius. The gastrocnemius should be separated along its borders from the soleus, in or- der to determine the line of division between them; it may then be cut across just below the union of its heads and the two halves reflected. In dissecting up the heads of the gastrocnemius, the strong character of its attachment will be seen. A synovial bursa is sometimes found between the muscle and the condyle on one or both sides, and a sesamoid bone is occasionally developed in the head attached to the outer condyle. The Plantaris Muscle arises from the outer condyle of the femur in common with the under part of the outer head of the gastrocnemius; it forms a short belly, from two to fbur inches in length, terminating in a long, slender tendon which crosses obliquely between the gastrocnemius and soleus, and passing downwards by the inner side of the tendo Achillis, is inserted by the side of that tendon into the calcancum. It is not always easy to separate it from the tendo Achillis at its lower part. The Soleus Muscle arises from the head and upper half of the fibula and from the middle of the tibia; it forms an elliptical- shaped belly, and joins the tendo AchilUs some distance below its commencement. A synovial bursa is placed between the tendo Achillis and the bone above its insertion, and a considerable inter- space, filled with fat and cellular tissue, exists between it and the muscles beneath. BACK OF THE LEG. 223 The tendo Achillis may be divided, and the soleus and plantaris entirely re- moved; in doing this, it must be remembered, that the vessels and nerves, covered in by a fascia, lie between this muscle and those below it. A stout layer of fascia covers in the deep muscles and vessels; this extends from the popliteal space to the ankle-joint, and is attached to the fibula on one side, and the tibia on the other. The popliteal artery will be found dividing into anterior and posterior tibial arteries, and the course of the anterior, to the point where it perforates the interosseous membrane, will now be seen. The posterior tibial artery descends the leg on the side of the tibia, and, at the lower part of its course, becomes comparatively superficial; it runs along the tendo Achillis, to the concavity formed by the internal malleolus and os calcis, where it divides into the plantar arteries, which will be seen in the dissection of the sole of the foot. It gives off in its course numerous muscular branches, some of which were divided in removing the superficial layer of muscles; others will be seen going to the deep layer ; a nutrient artery, to the tibia, may sometimes be found, if the sub- ject is well injected. The important branch of the posterior tibial artery, is the peroneal. The peroneal artery arises some distance from the commence- ment of the posterior tibial, and passes downwards along the inner border of the fibula; in the lower third of the leg, it divides into two branches : one of them, the anterior, perforates the interosseous membrane, and is distributed in front of the external malleolus ; the posterior division continues downward to the outside of the os calcis, where it breaks up into external calcanear branches. The peroneal and posterior tibial arteries present frequent variations of distribution and size ; one or the other is occasionally absent, and they sometimes communicate with each other by means of a short, though large, transverse anastomosis. The posterior tibial nerve accompanies the posterior tibial artery, lying first upon its inside, and then upon its outside. At the inner malleolus, it divides into two branches, internal and ex- ternal plantar. In its course, it gives off muscular branches, one of which accompanies the peroneal artery; at the heel, it gives off plantar cutaneous branches, distributed to the integument of the side of the heel. 224 ANATOMY OF THE LOWER EXTREMITY. The Popliteus Muscle is a short muscle-just below the knee-joint; arising from the outer side of the external condyle, it passes obliquely downwards, to be inserted into the surface of the tibia, above the oblique line, known as the popliteal. The Flexor Longus Digitorum Pedis arises from the sur- face of the tibia, below the popliteus, and passing behind the internal malleolus, through a sheath in the internal annular liga- ment, enters the sole of the foot, and divides into four tendons, inserted into the last phalanges of all the toes, except the great toe, as will be seen hereafter. The Flexor Longus Pollicis Pedis lies upon the outer side of the leg, and arises from the lower two thirds of the fibula, and from the interosseous membrane; its tendon curves around the internal malleolus, lying in a special sheath of the internal annular ligament, below the tubercle of the os calcis, and enter- ing the sole of the foot, is inserted into the last phalanx of the great toe. The posterior tibial nerve lies along the inner side of this muscle, and the peroneal vessels are in part concealed by it. The Tibialis Posticus Muscle lies between the two bones of the leg, and between the two muscles last described. It arises from nearly the whole length of both tibia and fibula, and from the interosseous membrane; its origin superiorly forms, as it were, two heads, between which passes the anterior tibial artery; its tendon curves around the internal malleolus, passing through a special sheath in the internal annular ligament, and enters the sole of the foot, to be inserted into the scaphoid and internal cuneiform bones. Along the outer border of the leg, and upon the fibula, will be found two muscles, the peroneus longus and brevis. The Peroneus Longus Muscle arises from the head and upper part of the surface of the fibula, and terminating in a long tendon, curves around the external malleolus, and through the sheath of the external annular ligament; entering the sole of the foot, it is inserted into the base of the metatarsal bone of the great toe. The musculocutaneous nerve lies between this muscle and the extensor longus digitorum. The Pekoneus Brevis Muscle lies beneath the preceding, and arises from the lower half of the outer surface of the fibula; SOLE OF THE FOOT. 225 its fibres are inserted in a penniform manner into a tendon which passes beneath the external annular ligament with the peroneus longus, and is inserted into the base of the metatarsal bone of the fifth toe. The Internal Annular Ligament confines the tendons which curve around the inner ankle from the back of the leg; it stretches across from the tip of the internal malleolus to the side of the os calcis, and contains three compartments, lined by synovial membrane. The External Annular Ligament stretches across from the tip of the external malleolus to the side of the os calcis, and consists of a single compartment lined with synovial membrane, through which pass the tendons of the peroneus longus and brevis. DISSECTION Xlll. SOLE OF THE FOOT. The dissection of the foot is a very difficult one; the density of the cuticle, the thickness of the fat and areolar tissue superficially, and the number and small- ness of the muscles, with the amount of aponeurotic structure which belongs to the region, render the dissection a slow and tedious process. A block should be put under the instep, and as the foot, by its own weight, offers no impediment to con- stant unsteadiness, it should be fixed to the table by hooks. An incision is to be made down the middle of the sole, from the heel to the commissure of the toes; this should penetrate to the plantar fascia; the integument, with the fat, should then be removed, and, as a preliminary step, this fascia should be cleanly dissected, and the deposits of fat removed from its interstices, wherever they exist, carefully look- ing out for the branches of nerves which so nearly resemble its fibres in color. The plantar fascia is a thick aponeurosis which expands over the whole sole of the foot, lying between the muscles and the adipose tissue beneath the integument; it is thicker in the centre than at the sides of the foot, and dividing into slips anteriorly, is attached to the base of the first phalanx of each toe by lateral processes, between which pass the flexor tendons; these are crossed by some transverse bands of fibres which sustain the rudimentary web of the commissures of the toes; between the slips, the nerves destined to the toes and the lumbricales muscles will be found. 15 226 ANATOMY OF THE LOWER EXTREMITY. The plantar fascia may be removed by dividing it transversely and dissecting up the two ends from their subjacent attachments; this will expose the muscles be- neath. In direct relation with the central portion of the plantar fascia is the flexor brevis digitorum. The Flexor Brevis Digitorum arises from the under side of the os calcis and from the plantar fascia; it divides into four tendons, which are inserted into the base of the second phalanx of the outer four toes; they are each perforated to permit the passage through them of the tendons of the long flexor, which is inserted into the last phalanx. The sheaths of the flexor tendons consist of transverse fibrous bands which hold the tendons down upon the phalanges; though similar to those of the fingers, they are not so distinct nor so well developed. The Abductor Pollicis Pedis lies upon the side of the great toe ; it arises by two heads, which are not, however, well-marked divisions ; one is from the internal annular ligament which covers in the vessels and tendons below the inner malleolus, the other from the inner tuberosity of the os calcis. Between these heads pass the plantar vessels, nerves, and tendons. It is inserted, after uniting with the tendon of the flexor brevis pollicis, into the base of the first phalanx of the great toe. The Abductor Minimi Digiti Pedis is placed along the outer edge of the foot; it arises from the external surface of the os calcis, and from the plantar fascia which covers it, and is inserted into the base of the first phalanx of the little toe. The flexor brevis digitorum is separated from the muscles on each side of it by strong intermuscular septa; the inner one of these is perforated by the internal plantar nerve and by the ten- don of the flexor longus pollicis; the outer one by the nerve and artery destined to the outer side of the little toe. The flexor brevis and abductor minimi digiti should be divided, and their two ends reflected; the tendons of the long flexor, with the plantar vessels and nerves, will then be exposed, and should be cleared from the superfluous areolar tissue which invests them. The posterior tibial artery, on entering the sole of the foot, divides into the internal and external plantar arteries. The internal plantar artery passes between the abductor pollicis and flexor brevis to the great toe; it gives off small muscular branches, and terminates in supplying the inner two toes. SOLE OF THE FOOT. 227 The external plantar artery is larger than the internal; it passes obliquely beneath the flexor brevis to the base of the fifth metatarsal bone, and then curves transversely across the foot, dipping beneath the deeper muscles, to the first interosseous space, which it penetrates to anastomose with the dorsalis pedis artery. The nerves of the sole of the foot are derived from the poste- rior tibial, which, at the inner malleolus, divides into external and internal plantar branches. The internal plantar nerve is the larger of the two, and runs along the edge of the abductor pollicis muscle, and divides opposite the base of the metatarsal bones, into four digital branches which supply, by bifurcating, both sides of the first, second, and third toes, and the inside of the fourth toe; it also gives off small muscular branches. The external plantar nerve accompanies the external plantar artery as far as the fifth metatarsal space,where it sends off a large muscular branch, and continues on in two divisions, which supply the outer edge of the foot, the little toe, and the half of the next, which is unsupplied by the internal plantar. In the second layer of muscles are found the tendons of the flexor longus digitorum and flexor longus pollicis of the back of the leg (p. 224). The tendon of the flexor longus digitorum passes to the middle of the sole of the foot, and is there joined by a tendinous process from the flexor longus pollicis and by the musculus accessorius, and divides into four tendons for the outer four toes; these perforate the tendons of the flexor brevis, and are held down by ligamenta brevia, like those of the tendons of the fingers (p. 138). The Lumbricales Muscles are four small muscles arising from the tendons of the long flexor, and inserted into the expan- sions of the extensor tendons and the inner sides of the first pha- langes, of all the toes except the great toe. They are subject to variations. The Musculus Accessorius, or Massa carnea Jacobi Sylvii, arises by two heads, one from the concave, inner side of the os calcis, and the other from its under surface, and is inserted into the tendon of the flexor longus digitorum, just as it separates into its four digital divisions. The tendons of the flexor longus must be divided, and, with their accessory muscles, reflected. The Flexor Brevis Pollicis Pedis arises from the cuboid and internal cuneiform bones; it lies upon the metatarsal bone of the 228 ANATOMY OF THE LOWER EXTREMITY. great toe, and is inserted by two heads into the base of its first phalanx; the outer head joins with the tendon of the abductor, and the inner head with that of the adductor pollicis; a sesamoid bone is usually found in each of these heads; the tendon of the flexor longus pollicis passes between them. The Adductor Pollicis Pedis is placed obliquely in the sole of the foot; it arises from the cuboid bone, the heads of the third and fourth metatarsal bones, and from the sheath of the tendon of the peroneus longus; it forms a short belly, and is inserted with the inner head of the flexor brevis pollicis into the base of the first phalanx of the great toe. A sesamoid bone is usually found in the insertion of its tendon. The Flexor Brevis Minimi Digiti Pedis arises from the base of the metatarsal bone of the fifth toe and the sheath of the tendon of the peroneus longus, and is inserted into the base of the first phalanx of the little toe. The Transversalis Pedis is a thin layer of muscular slips lying transversely across the anterior portions of the metatarsal bones; it arises from the heads of the metatarsal bones of the four lesser toes, and is inserted into the tendon of the adductor pollicis; sometimes there is but one slip; there are rarely so many as four. The adductor pollicis and flexor brevis minimi digiti are to be divided near their origin, and turned forwards on to the toes; this will expose the plantar arch. The plantar arch is the continuation of the external plantar artery from the base of the fifth metatarsal bone to its anastomosis with the communicating branch of the dorsalis pedis; it lies upon the interosseous muscles, and gives off four digital branches to the toes; the first goes to the outer side of the little toe; the others, dividing at the commissures, supply the contiguous sides of the outer three toes and the inner side of the second. At the base of the interosseous spaces, as well as at the anterior part, the digital arteries send small branches called posterior and anterior perforating, to the interosseous arteries of the dorsalis pedis. The communicating branch of the dorsalis pedis enters the sole of the foot, and, uniting with the plantar arch, supplies both sides of the great toe and the inner side of the next. The Plantar Interosseous Muscles are three in number; they arise from the under sides of the metatarsal bones, and are LIGAMENTS OF THE PELVIS, ETC. 229 inserted into the inner sides of the bases of the first phalanges of the outer three toes, and into the expansions of the extensor tendons. The tendon of the tibialis posticus (p. 224) may now be traced to its termination; it passes forwards over the articulation of the astragalus and scaphoid bones to be inserted into the latter, and also into the internal cuneiform bone ; a sesamoid bone is usually found in its tendon. The tendon of the peroneus longus (p. 224) passes obliquely across the foot to the metatarsal bone of the great toe; as it turns round the cuboid bone its tendon becomes thickened and fibro- cartilaginous, and sometimes contains a sesamoid bone; it is en- veloped with a sheath formed by the ligaments of the tarsal bones, and lined by a synovial membrane. DISSECTION XIV. LIGAMENTS OF THE PELVIS AND LOWER EXTREMITY. The pelvis is connected with the vertebral column by liga- ments similar to those uniting one vertebra to another, with the addition of two special ligaments, the lumbo-sacral and the ilio- lumbar. The lumbo-sacral ligament is a stout triangular bundle of fibres springing from the tip of the transverse process of the last lum- bar vertebra, and expanding, fan-shaped, to be inserted into the posterior part of the upper border of the sacrum. The ilio-lumbar ligament extends between the tip of the trans- verse process of the last lumbar vertebra and the crest of the ilium, just above the sacro-iliac articulation. The sacrum and the coccyx are united by an anterior and pos- terior common ligament, and by intervening fibro-cartilaginous disks ■ in adults, the bones are, however, usually co-ossified. The sacrum and ilium are united by cartilage and by anterior and posterior sacro-iliac ligaments at the sacro-iliac synchondrosis, and by the sacro-ischiatic ligaments inferiorly. 230 ANATOMY OF THE LOWER EXTREMITY. The anterior sacro-iliac ligament is a transverse band of fibres in front of the articulation, attached to the bone on either side. The posterior sacro-iliac ligament is composed of stout bundles of fibres passing between the first two bones of the sacrum and the rough surface at the posterior border of the os innominatum. The long sacro-ischiatic ligament passes from the side of the sacrum and coccyx to the tuberosity of the ischium. The short sacro-ischiatic ligament arises from the side of the sacrum and coccyx, and is inserted into the spine of the ischium. These two ligaments convert the space between the sacrum and os innominatum into two apertures, called the sacro-ischiatic foramina, through which issue the nerves, arteries, and muscles of the interior of the pelvis. The union of the pubic bones in front is called the symphysis pubis. The anterior pubic ligament consists of horizontal and oblique fibres, interlacing in front of the articulation. The periosteum constitutes the posterior pubic ligament. The superior pubic ligament crosses the surface of the bones superiorly, and is confounded with the tendinous insertions of the abdominal muscles. The sub-pubic ligament is a fibrous arch attached to the bones of the pubis inferiorly, and losing itself at each side on the ramus of the ischium. The inter-articular fibro-cartilage, seen on opening the symphy- sis, is composed of concentric layers of fibres firmly attached to the opposed surfaces of the bones, and projecting a little beyond their borders. At the posterior part, a cavity, containing a fluid like the synovial, and of variable size, will be found separating the cartilage into two lateral halves ; this cavity is said to increase in size during pregnancy. The obturator ligament or membrane is a tendino-fibrous mem- brane, stretching across the thyroid foramen, and which closes it in its entire extent, except at the upper part, where the obturator artery and nerve pass out of the pelvis. The Coxo-femoral Articulation, or Hip Joint, in which the head of the femur is received into the cotyloid cavity of the LIGAMENTS OF THE PELVIS, ETC. 231 os innominatum, is maintained by a capsular and an inter-articular ligament. The capsular ligament is attached to the circumference of the acetabulum, and to the inter-trochanteric line of the femur ante- riorly, and the neck of the bone posteriorly. It is strengthened anteriorly by a band of fibres, called the iliofemoral ligament, which passes from the anterior inferior spinous process of the ilium, to the inter-trochanteric line. The capsular ligament is to be divided transversely, and the head of the femur dislocated from its socket, to see the inter-articular ligament. The inter-articular ligament, or ligamentum teres, extends from the depression in the head of the femur to the borders of the notch in the acetabulum. The cotyloid ligament is a fibro-cartilaginous band attached to the margin of the acetabulum, the cavity of which is surrounded and deepened by it. The transverse ligament is a band of fibres continuous with those of the cotyloid ligament, which extends across the notch of the acetabulum, and protects the vessels passing beneath it to the inter-articular ligament and head of the femur. The head of the femur is not entirely covered with cartilao-e, a portion of it around the depression in its centre being divested of that covering. In the cotyloid cavity there is also a depres- sion which has no cartilage; this is occupied by a mass of fat, sometimes called the synovial gland of Havers. The Tibio-femoral Articulation, or Knee Joint, is in- vested by a capsule, and by anterior, posterior, external, and internal ligaments. The capsule is a firm membrane which surrounds the heads of the bones, and fills the intervals of the stronger, special liga- ments. The external lateral ligament is a rounded bundle of fibres, ex- tending between the external condyle and the head of the fibula; a second bundle is sometimes found behind this one, and called the short external lateral ligament. The internal lateral ligament is attached to the internal con- dyle above, and the inner tuberosity of the tibia below ; its limits 232 ANATOMY OF THE LOWER EXTREMITY. are not distinctly marked; the inferior internal articular artery, and the tendon of the semi-membranosus, pass beneath it. The anterior ligament, or ligamentum patella, is attached to the lower border of the patella above, and the tubercle of the tibia below ; a bursa will be found beneath its insertion into the tubercle. The posterior ligament, or ligamentum posticum Winslowii, is formed chiefly by fibres of the tendon of the semi-membranosus, which pass across the joints to the outer condyle; a deeper set of fibres is continuous with the general capsule. The knee-joint is to be opened, by an incision along each side and across the front, above the patella; the patella and its ligament are to be turned downwards; this exposes the synovial membrane and inter-articular ligaments. The synovial membrane covers the cartilages of the bones, and all the inter-articular structures; it forms a pouch on each side of the patella, extending above and below it a distance some- times as great as two inches ; posteriorly it sends a pouch between the head of the popliteus muscle and the tibia. A fold of the synovial membrane, called the mucous ligament, extends from be- tween the condyles to the fat below the patella; this is continued outwards to the sides of the patella, under the name of the alar ligament. The crucial ligaments are two strong bands, the anterior of which, arising from the depression in front of the spine of the tibia, goes to the inner surface of the external condyle, and the posterior from the depression behind the spine to the internal condyle ; the internal is larger than the external. The respective insertions of the crucial ligaments are difficult to remember; the initial letters of the words, anterior, external, posterior, internal, manufacture the word aepi, from which the memory may derive assistance. The semi-lunar fibro-cartilages are two crescentic plates of car- tilage placed upon the margins of the head of the tibia, and attached externally to the capsule of the joint; they are thick along their convex border and thin at the concave, being hollowed out to receive the condyles of the femur; they are connected anteriorly with the front of the tibia, and posteriorly with its spin- ous process. The internal cartilage forms the segment of a larger circle than the external, and is more ovoidal in shape. The transverse ligament unites these cartilages anteriorly; sometimes it hardly exists. LIGAMENTS OF THE PELVIS, ETC. 233 The tibia and fibula are articulated together at their two ends, and connected between their shafts by an interosseous mem- brane. The union between the bones superiorly is very simple, and consists of anterior and posterior bands from the tuberosity of the tibia to the head of the fibula. Inferiorly-, an anterior band crosses in front from the fibula to the tibia, and a posterior one is similarly disposed behind the joint; an inferior ligament closes the space between the ends of the bones below, and may be seen by forcibly tearing them apart. The interosseous membrane is attached to the contiguous sides of the shafts of the tibia and fibula, and separates the muscles of the back from those of the front of the leg; its fibres are directed downwards and outwards, and are crossed by a few passing in the opposite direction ; they are deficient above, where the ante- rior tibial artery enters, and below, at the point where the ante- rior peroneal artery comes forward from the back of the leg, to be distributed on the tarsus. The Tibio-tarsal Articulation, or Ankle Joint, is formed by the fibula, the tibia, and the astragalus, and is main- tained by four ligaments, anterior, posterior, external, and in- ternal. The anterior ligament, is a thin membranous layer, extending from the front of the tibia to the upper part of the astragalus, and continuous by its sides with the lateral ligaments. The internal lateral, or deltoid ligament, expands, fan-shaped, from the tip of the inner malleolus, to be inserted into the side of the astragalus, os calcis, and scaphoid bone. This ligament is covered in by the internal annular ligament (p. 225), and the tendons which pass through it. The external lateral ligament, consists of three strong fasciculi; the anterior of which passes from the anterior border of the mal- leolus, to the surface of the astragalus in front of it; the middle descends from the tip of the malleolus to the os calcis, and the posterior from the posterior border of the malleolus, horizontally backwards, to the posterior surface of the astragalus. 234 ANATOMY OF THE LOWER EXTREMITY. The tarsal bones of the foot are united by dorsal, plantar, and interosseous ligaments. The dorsal ligaments, unite each tarsal bone with those contig- uous to it; several strong bands pass forwards from the deep fossa between the astragalus and os calcis, to the scaphoid and cuboid bones, under the name of calcaneo-cuboid and astragaloscaphoid ligaments. The plantar ligaments also consist of small bands uniting the contiguous bones, with the addition, however, of two others of large size and great strength. The inferior calcaneoscaphoid ligament unites the os calcis and the scaphoid bone, forming part of the cavity which receives the rounded head of the astragalus; the tendon of the tibialis posticus crosses this ligament. The long calcaneo-cuboid ligament passes from the under surface of the os calcis to the rough ridge on the under part of the cuboid bone; some of its fibres continue over the tendon of the peroneus longus, forming a sheath for it, and are inserted into the base of the third and fourth metatarsal bones; these last-named fibres are sometimes called the ligamentum longum planta, and the shorter ones the ligamentum breve planta. The interosseous ligaments are five in number, and are strong bands intervening between contiguous surfaces of adjoining bones. The calcaneo-astragaloid lies in the fossa between the os calcis and astragalus, and can only be seen by a longitudinal section of the two bones, when it will be found as a short stout band, attached to a depression in each bone. Another interosseous ligament exists between the articulating surfaces of the cuboid and scaphoid bones, and three others between the three cunei- form and cuboid bones. The bases of the metatarsal bones are united by dorsal, plantar, and interosseous ligaments; the interosseous ligaments are to be demonstrated by tearing the bones apart, when the dissection is completed; they are only found between the outer four bones, that of the great toe not being united with the others. The heads of the metatarsal bones are connected inferiorly by transverse metatarsal ligaments. The metatarsophalangeal articulations are maintained by two lateral ligaments and an inferior ligament, the expansion of the extensor tendon supplying the place of a superior one. LIGAMENTS OF THE PELVIS, ETC. 235 The phalanges are united to each other by two lateral liga- ments and an inferior ligament, and by the expansion of the extensor tendon superiorly. The joints between the phalanges are sometimes very indistinct, and occasionally co-ossified. The ligamentous arrangements, and the insertions of the tendons are precisely the same as in the fingers, and are much more satisfac- torily studied in the hand, the description of which is given at p. 145. PECULIARITIES IN the ANATOMY OF THE FCETUS. Upon the foetus may be demonstrated almost all the anatomy of the human sys- tem ; the points in which it differs from that of adults will alone be noticed. The full-grown foetus weighs about seven pounds, and is seven- teen inches in length, or thereabouts; the umbilicus is situated from a quarter to half an inch below the middle of the body. The external genital organs are largely developed, especially the labia minora in the female, which project beyond the labia ma- jora; in the male, the prepuce is adherent to the glans penis, constituting a state of phymosis. The muscles are pale, and of a softer texture than when more developed, and are covered in with a dry and granular fat, easily detached from them. The umbilical cord is composed of two umbilical arteries, and an umbilical vein, imbedded in a soft, semi-transparent substance, called the Whartonian gelatine. Within the abdomen, the arte- ries are called the hypogastric. The abdomen is to be opened in such a way as to avoid injuring the vessels which diverge upwards and downwards from the umbilicus. The Hypogastric Artery is the internal iliac artery of adult life ; it is larger than the external iliac, and may be traced from the common iliac artery upwards, along the sides of the urinary bladder and urachus, to the anterior wall of the abdo- men, upon which it ascends to the umbilicus, where the two arteries come together, escape from the abdomen with the umbilical vein, and coil around it in the umbilical cord, until they reach the pla- centa. After the cessation of placental circulation, this artery ANATOMY OF THE F03TUS. 237 becomes impervious from the side of the bladder upwards, and is converted into a fibrous cord (p. 190) ; an inch or so of its com- mencement still continues pervious, and gives origin to the supe- rior vesical artery. The Umbilical Vein runs from the umbilicus along the free margin of the suspensory ligament of the liver to the transverse fissure of that organ ; it there divides into two branches, one of which continues on to join the vena cava inferior; this is the ductus venosus ; the other and larger branch turns to the right, along the transverse fissure, and joins the portal vein. After the cessation of placental circulation, the umbilical vein and ductus venosus become converted into a fibrous cord, the former becom- ing the round ligament of the liver. The Liver occupies the whole upper part of the abdomen; it is of a dark, mahogany color, and its lobes are nearly equal in size. After birth, it rapidly diminishes in bulk ; and, at the age of five or six, attains the proportions maintained during the rest of life. The Kidneys present a lobulated appearance, and are rela- tively larger than in the adult. The supra-renal capsules are also of large size. The Bladder is long and conical, and is connected superiorly with the umbilicus by a fibrous cord called the urachus. This is an obliterated tube which during the early part of intra-uterine life connected the bladder with one of the fotfal membranes called the allantois. v The Intestines are small in calibre, and are filled with a dark green substance called meconium. The small intestines are devoid of valvulae conniventes, or these are but imperfectly de- veloped. The appendix of the caecum is long and of large size, and seems like a constricted continuation of the caecum itself. The Testes, in the early part of foetal life, are situated in the lumbar region, behind the peritoneum. About the fifth month they begin to descend to the scrotum, but not unfrequently they may be found delayed in some part of their course at the time of birth. Connected with the lower end of the testicle and epidi- dymis is a band composed of areolar and muscular tissue, called the gubernaculum testis, which serves as a guide and assists in their gradual descent; it extends through the inguinal canal, 238 ANATOMY OF THE F03TUS. and is attached to the front of the pubes and the bottom of the scrotum. Before the testicle enters the internal inguinal ring, a small pouch of peritoneum will be found protruding at that point; this, under the name of processus vaginalis peritonei, precedes the testicle in its course through the inguinal canal, and enters the scrotum in advance of the gland. The neck of this pouch, by which it is connected with the general peritoneal cavity, becomes gradually obliterated after birth, whilst the pouch itself remains as an independent serous sac, under the name of tunica vaginalis testis. The ovaries in the female are likewise placed in the lumbar region, and gradually descend to the pelvis. A pouch of perito- neum, analogous to the processus vaginalis of the male, accom- panies the round ligament of the uterus for a short distance into the inguinal canal, and is called the canal of Nuck. On opening the thorax there is found in the anterior mediasti- num, and extending upwards upon the trachea into the neck, a narrow, elongated body, lobulated, pinkish in color and soft in texture ; this is the Thymus Gland. It consists of two lateral lobes enveloped in an areolar capsule. A central cavity, contain- ing a milky fluid, exists in each lobe; it has no duct or outlet The thymus gland increases in size for about two years; it then dwindles, and becoming converted into a fatty mass, at the age of puberty has nearly disappeared. The Lungs are small, and lie packed in the posterior part of the thorax. Previous to respiration they consist of a dense gland- like substance. Subsequently to respiration they are of a pinkish, spongy structure, expanding and completely filling the pleural cavity. The Heart is well developed in point of size, but the septum between the auricles is incomplete, being perforated by a large opening called the foramen ovale. A communication will also be found between the left pulmonary artery and the aorta, just beyond the origin of the brachio-cephalic vessels, by a short trunk called the ductus arteriosus; this degenerates into a fibrous cord shortly after birth, and the foramen ovale usually becomes oblitr erated. The Eustachian valve is of large size, and seems to be a continuation upwards of the anterior border of the inferior cava towards the foramen ovale. ANATOMY OF THE F03TUS. 239 The Fcetal Circulation presents peculiarities. The oxy- genized blood from the placenta is brought by the umbilical vein to the inferior vena cava, where it of course mixes with the impure blood from the lower extremities; entering the right auri- cle, its current is directed by the large Eustachian valve towards the foramen ovale, through which it passes into the left auricle. The blood from the head and upper extremities, which is returned by the superior vena cava as venous blood, enters the right auri- cle and passes by the auriculo-ventricular opening into the right ventricle ; the crossing of these two currents in the right auricle is permitted by the construction of the Eustachian valve, though, to a certain extent, the two streams must intermingle. We thus see that the blood brought to the right auricle has two sources of exit, viz: the foramen ovale and the auriculo-ventricu- lar orifice. By following the blood from the cavities into which these orifices open, as if it had started originally from these points, we shall at once comprehend the foetal circulation. Thus, that from the right ventricle must enter the pulmonary artery which goes to the lungs; but the lungs are solid and impervious, and nature has therefore provided an exit from it by the ductus arteriosus, through which it is carried to the aorta beyond the brachio-cephalic branches, and so to the trunk and lower extremi- ties. Then again, the blood which is in the left auricle can go only to the left ventricle, and from there it must go to the aorta. This portion of the blood being that most richly oxygenized, is able to enter the brachio-cephalic trunks, which the other current could not do, and supply the important parts to which they are distrib- uted. Farther on in the aorta it joins with the current from the ductus arteriosus, supplies the trunk and lower extremities, and is returned to the placenta by the hypogastric arteries. INDEX. 0= The letter [o] prefixed to any of the following figures refers to the origin, [c] to the course, and [d] to the distribution of any nerve or vessel which may happen to be described on different pages. Abdomen, 146. arteries of, 159. superficial fascia of, 147, 152. Abdominal regions, 156. Acervulus, 76. Acini, 174. Allantois, 195. Ampulla?, 82. Andersch, ganglion of, 24. Annulus albidus, 62. ovalis, 101. Anti-helix, 2. Anti-tragus, 2. Aorta, abdominal, 161. arch of, 42, 98. ascending, 98. descending, 98. sinuses of, 103. thoracic, 104. transverse, 98. Aponeurosis epicranial, 3. pharyngeal, 47. temporal, 12. vertebral, 112. Apparatus Iigamentosus colli, 59. Appendices epiploicae, 167. Appendix of the auricles, 99. of the testicle, 200. vermiformig easci, 167. Aqueduct of Sylvius, 75. Aqueductus cochleae, 83. vestibuli, 82. Aqueous humour, 63. Arachnoid of the brain, 64. of the spinal cord, 118. Arbor vitae of the cerebellum, 78. of the uterus, 203. Arch, aortic, 42, 98. crural, 180. palmar, deep,, 138. superficial, 136. plantar, 228. Arches of the palate, 48. Arciform fibres, 69. Arnold's ganglion, 35, 50. Artery, accessory hepatic, 162. acromial, inferior, 89- anastomotica magna, of arm, 92. of thigh, 210. angular, 10. aorta, abdominal, 161. arch of, 42. thoracic, 104. articular of the knee, 217. auditory, internal, 84. auricular, anterior, [d] 2, [o] 32. 16 • Artery, auricular, posterior, [d] 2, [o] 32. axillary, 87. azygos articular, 217. basilar, 65. brachial, 90. brain of the, 65. bronchial, 104. buccal, 36. bulb of the, 187,188. calcancar, 223. carotid, common, [c] 29, [o] 42. external, 30. internal, [o] 38, [c] 17, [d] 66. temporal portion of, 50. carpal, radial, 127. ulnar, 128. centralis retinae, 19. cerebellar, inferior, 65. superior, 65. cerebral, anterior, 66. middle, 66. posterior, 65. ciliary, 19. circumflex, anterior, 89. external, [o] 209, [d] 212, 215. superficial, 179. internal, [o] 209, [d] 215. ilii, [o] 184, [d] 150. posterior, 89. coeliac, 161. colica, dextra, 162. media, 162. sinistra, 163. comes nervi ischiatici, 213. phrenici, 95. communicating, anterior, 66. of the foot, 221. of the hand, 136. posterior, 65, 66. coronary of the heart, [d] 99, [o] 103. of the lips, 10. cvstic 161. dental, inferior, [o] 36, [d] 9 superior, 36. digital of the foot, 221, 228. of the hand, 136. dorsalis, hallucis, 221. nasi, 19. pedis, [o] 220. [d] 221. penis, 187. dorsalis, pollicis, 133. scapulae, 123. 242 INDEX. Artery, epigastric, [c] 151, [o] 184. superficial, [c] 147, [o] 178]. superior, 96. ethmoidal, 18. facial, [o] 31, [d] 10. femoral, 208. frontal, [o] 18, [d] 6. gastric, 161. gastro-duodenalis, 161. epiploica dextra, 161. sinistra, 162. gluteal, [o] 191, [d] 212. hemorrhoidal, external, 185. inferior, 190. middle, 190. superior, [o] 63, [c] 191. hepatic, 161. accessory, 162. . hyoid, 31. hypogastric, [o] 190, [c] 236. ileocolic, 162. iliac, common, 164. external, 184. internal, 189. ilio-lumbar, [o] 191, [d] 184. infra-orbital, [o] 36, [d] 7. innominata, 42. intercostal, 105. anterior, 95. external, 105. posterior branches of, 113. superior, 44. interosseous, 128. anterior, 129. of foot, 221. posterior, 131. ischiatic, [o] 190, [d] 213. labial, inferior, 10. lachrymal, 18. laryngeal, 31. lateral sacral, 191. lateralis nasi. 10 Ungual, [ol 31, [d] 53. lumbar, 165. posterior branches of, 113. malleolar, 220. mammary, external, 89. internal, [o] 45, [d] 95. masseteric, 36. maxillary, iuternal, 36. mediastinal, 96. meningea, anterior, 17. inferior, [o] 32, [d] 17. media, [o] 36, [d] 17. parva. [o] 36, [d] 17. posterior, [o] 36,[d] 17. mesenteric, inferior, 163. superior, 162. metacarpal, 133. metatarsal, 221. musculo-phrenic, 96. mylo-hyoid, 36. nasal, [o] 18, [d] 5. nutrient of femur, 209. , nutrient of tibia, 223. obturator, [o] 184, 190, [d] 211. occipital, [o] 31, [d] 5,113. oesophageal, 105. ophthalmic, 18. orbitar, 32. ovarian, [o] 164, [c] 191, [d] palatine, posterior, 36. palpebral, [o] 18. [d] 5. pancreatico-duodenalis, 161. parotidean, 32. perforating of the thigh, [o] 209, [d] 215. of the hand, 139. of the foot, 228. pericardiac, 96. perineal, superficial, 185. peroneal, 223. anterior, 220. pharyngeal, ascending, 32, 38 phrenic, [o] 161, [d] 178. plantar external, 227. internal, 226. popliteal, 217. posterior scapular, [o] 44, [d] 113, 123. princeps cervicis, [o] 31, [d] 113. pollicis, 138. profunda cervicis, [o] 44, [d] 113. of the thigh, 209. superior, 91. inferior, 91. pterygoid, 36. pterygopalatine, 36. pudic external, superficial, 179. deep, 179. internal, [d] 187, [o] 190, [c] 213. pulmonary, 98. pyloric, 161. radial, [o] 126, [cl 133, [d] 138. radialis indicis, 138. ranine, 53. recurrent interosseous, 131. radial. 126. tibial, 220. ulnar anterior, 128. posterior, 128. renal, 163. sacral, lateral, 191. sacra media, 165. scapular, posterior, [o] 44, [d] 113,123. sigmoid, 163. spermatic, 164. spheno-palatine, 36. spinal, 105. splenic, 162. stylo-mastoid, 32. subclavian, 42. submental. 33. subscapular, [o] 89. [d] 121,122 superficialis cervicis, 44, 113, 115. volte, [o] 127, [d] 135. supra-orbital, 18. supra-renal, 163. INDEX. 243 Artery, supra-scapular, [o] 44, [dl 113, 122. sural, 217. tarsal, 221. temporal, [o] 32, [dl 12. anterior, 13. deep. 36. middle, [o] 32, [d] 13. posterior, 13. thoracic, internal, 108. thoracica acromialis, 89. axillaris, 89. inferior, [o] 89, [d] 121. superior, 89. thyroid inferior, [o] 44, [d] 30 lowest, 44. middle, 42, 44. Neubauer, of, 44. superior, [o] 31. [d] 30. tibial anterior, [ol 217, [dl 220, [c] 223. posterior, [o] 217, [dl 223. transversalis cervicis, 44. perinei, 185. transverse facial, [o] 32, [dl 10. tympanic, 36. ulnar, 128. umbilical, 236. uterine, [o] 191. vaginal, [o] 191. vasa brevia, 162. vertebral, [o] 43. [c] 58, [dj 65,17. posterior branches of, 113. vesical inferior. 190. middle, 190. superior, 190. Vidian, 36. Articulations, acromioclavicular, 143. carpo-nietacarpal, 145. costo-vertebral, 140. coxo-femoral, 230. of the ribs with the ster- num, 140. metacarpophalangeal, 145. phalangeal, 145. sternal, 140. sterno-clavicular, 40. temporo-maxillary, 46. tibio-femoral, 231. tibio-tarsal, 233. Arytenoid cartilages, 56. Auditory canal, 79. Auricle, right. 100. left, 102. Auriculo-ventricular openings, 101, 102. Axilla, 87. Axis coeliac, 161. thyroid, 43. Bartholinus's glands, 202. Base of the brain, 69. Bichat, fissure of, 74. Bifurcation of the trachea, 98. Bi iary ducts, 159. Bladder, 195. fcetal, 237. Bone, hyoid, 55. Bone, spongy, 51. inferior turbinated, 51. turbinated, 51. Brain. 69. Bronchi, 98. Brunner's glands, 168. Bulb of corpus spongiosum, 19". olfactory, 20. Bulbous portion of urethra, 199. Caecum, 167. Calamus scriptorius, 77 Calyx of the kidney, 176. Canal, crural, 181. Fontana, of, 62. inguinal, 153. lachrymal, 5. Nuck, of, 154. Petit, of, 63. semicircular, 82. Capsule of Glisson, 174. of the knee-joint, 231. Capsules, supra-renal, 174. Caput coli, 167. galinaginis, 198. Cartilage alar, 8. inter-articular of clavicle, 40. of jaw, 46. of pubes, 230. of wrist, 145. lateral, 8. of nose, 8. of Santorini, 56. semilunar, 232. sesamoid, 8. Caruncula lacrymalis, 5. Carunculae myrtiformes, 202. Casserian ganglion, 22. Cauda equina, 119. Cava, vena, inferior, 97. superior, 41, 97. Cavity, preperitoneal, 151. visceral, 156. Centrum ovale majus, 71. minus, 71. Cerebellum, 76. Cerebrum, 69. Cerebro-spinal fluid, 65, 118. Cerumenous glands, 3. Cervical ganglia, 39. Chambers of the eye, 63. Chordae tendineae, 101. vocales, 55. Willissii, 14. Choroid, 62. plexus of fourth ventricle, 78. lateral ventricle, 72. third ventricle, 74. Ciliary ligament, 62. processes, 62. Circle of Willis, 66. Circulation, foetal. Clitoris, 201. Cochlea, 83. Coeliac axis, 161. Colon. 167. Columnae carneae, 101. Columns of Morgagni, 194. 244 INDEX. Columns of spinal cord, 120. of the vagina, 202. Commissure of spinal cord, 120. Commissures, 75. Concha, 2. Conjoined tendon, 149,150. Conjunctiva, 5. Convolution of corpus callosum, 71- Convolutions, 70. Cord, spermatic, 200. Cornea 62. Cornua of lateral ventricles, 72. Corona glandis, 198. Coronary valve. 100. Corpora albicantia, 70. Arantii, 102, 103. cavernosa, 197. quadrigemina, 76. Corpus callosum, 70, 7L fimbriatuui, 73, 204. geniculatum, 75. olivare, 69. pyramidale, 68. restiforme, 69. rhomboideum, 78. spongiosum, 197. striatum, 72. Corpuscles of the spleen, 170. Cortical substance of brain, 71. of kidney, 176. Covered band of Reil, 71. Cowper's glands, 187. Cranial nerves, [c] 20, [o] 67. Cribriform fascia, 179. Cricoid cartilage, 56. Crico-thyroid membrane, 56. Crista of the vestibule, 82. Crura cerebelli, 69, 77. of the diaphragm, 177. of the fornix, 73. Crus cerebri, 69. penis, 187 Crural arch, 180. canal, 181 septa of, 181. ring, lb'0. Crystalline lens, 63. Cuneiform cartilages, 66. Cupola, 83. Cystic duct, 173. Dartos, 199. Detrusor urinae, 195. Decussation of auterior pyramids, 69. Diaphragm, 177. larger muscle, of the, 177. lesser, 177. Duct, cystic, 169,173. hepatic, 159,173. pancreatic, 171. prostatic, 198. thoracic, [dl 41, [cl 107, [o]178. Ductus arteriosus, 98, 238. choledochus communis, 159, 173. communis ejaculatorius, 196. lymphaticus dexter, 41, 107. venosus, 237. Duodenum, 167, 168. Dura mater of the brain, 13. of the spinal cord, 118. Ear, external, 1. internal, 81. middle, 79. Ejaculatory duct, 196. Eminentia teres, 78. Encephalon, 66. Endocardium, 100. Epididymis, 200. Epigastric region. 157. Epiglottidean gland, 56. Epiglottis. 56. Eustachian tube, 48, 80. valve, 100. Eye, 60. Eyelids, 5. Falciform border. 179. Fallopian tubes, 204. Falx cerebelli. 16. cerebri, 14. Fascia, cervical, 25. cribriform, 179. deep, 179. iliaca, 180. infundibuliform of inguinal canal, 153. of crural canal, 180. lata. 179. leg, of the, 218. lumborum, 111. obturator. 192. palmar, 134. plantar, 225. pelvic, l9'2. perineal, 186. propria. 182. re to-vesical. 192. spermatic, 148, 153. superficial of abdomen, 147, 152. of thish, 178. transversalis, 153. Femoral heruia, 178. Fenestra ovalis, 79. rotunda, 79- Fibres, arciform, 69. inter-columnar, 14S. 152. „ Fibro cartilage, inter-articular of the cla- vicle, 40. of the jaw, 46. of the knee, 232. of the wrist, 145. Filum terminale, 118. Fimbriated extremity of Fallopian tube, 204. Fissura Glasseri, 80. Fissure of Bichat, 74. of Sylvius, 66, 70. transverse of the brain, 74. Fissures of the spinal cord, 120, 8. of the liver, 172. Floating kidney, 177. Fluid, sub-arachnoid, 65, 11. Foetal circulation, 239. INDEX. 245 Foetus, anatomy of, 236. Fold, recto-vesical, 188. recto-uterine, 188. semilunar of Douglass, 151. vesico-uterine. 188. Follicles of Lieberkuhn, 168. Foramen caecum, of brain, 68. of tongue, 52. commune anterius, 75. posterius, 75. Munro, of, 72, 75. ovale, 2.38. Soemmering, of. 63. Winslow, of, 158. Foramina Thebesii, 100. Fornix, 73. Fossa, inguinal. 154. innominata, 2. ischio-vectal, 185. navicularis, 199. ovalis, 101. scaphoid, 2. Fourchette, 201. Fovea hemispherica, 82. semi-elliptica, 82. Frenum epiglottidis, 52. of lips, 45. of tongue, 52. of prepuce, 198. Gall bladder, 173. Ganglia, cervi. al, 39. lumbar, 165. sacral, 189. semilunar, 161. thoracic, 106. Ganglion, Andersch, of, 24. Arnold's, 35, 50. Casserian, 22. cervical inferior, 39. middle, 39. superior, 44. jugulare, 24. lenticular, 21. Meckels, 50. otic, 35, 50. petrosum, 33. of the root. 24. semilunar, 161. spheno palatine, 50. sub-maxillary, 34. thyroid, 39. Genu of the corpus callosum, 70, 71. Gimbernat's ligament 180. Gland, epiglottidean, 56. lachrymal. 6. pineal, 76. pituitary, 17. prostate, 196. thymus, 96, 238. Glands, agminated, 168. Bartholine's, 202. bronchial, 99. Brunner'e, 168. ceruminous, 3. Cowper's, 1H7. , duodenal, 168. inguinal, 147, 179. Glands, labial, 8. Lieberkuhn's, 168 mammary, 86. mesenteric, 163 Meibomian, 5. Pacchionian, 14. parotid, 11. Fever's, 168. solitary, 168. sub-lingual, 52. sub-maxillary, 33. synovial of Havers, 231. tracheal, 56. Tyson's, 198. Glans, clitoridis, 201. penis, 198. Glisson's capsule, 174. Graafian vesicles, 204. Gubernaculum testis, 237. Guthrie's muscle, 193. Gyri, 70. Gyrus fornicatus, 71. Hamulus laminae spiralis, 83. Heart, 97, 99. foetal, 238. He'icotrema, 83. Helix, 2. Hemispheres of the brain, 70. Hepatic duct, 173. Hey's ligament, 180. Hernia congenital, 155. crural, 178 direct, 154. encysted. 155. femoral, 178. inguinal, 152. oblique, 155. caecum, of the, 158 Hesselbach, triangle of, 154. Hilton's muscle, 54. Hilus of the kidney, 175. of the spleen, 170. Hippocampus major, 73. minor, 73. Horner's muscle, 6. Horseshoe kidney, 176. Hyaloid membrane, 64. Hyoid bone, 55. Hymen, 202 Hypochondriac region, 157. Hypogastric region, 157. Ileo-caecal valve, 167. Ileum, 167. Iliac region, 180. Incisura cerebelli, 77. Incus, 81. Infundibulum of the brain, 70. of the heart, 101. of the kidney, 176. Inguinal canal, 153. fossae, 154. region, 152, 157 Inter-articular cartilage of the clavicle, 40. of the jaw, 46. of ihe wrist, 145. 246 INDEX. Iuter-columnar fibres, 148, 152. Inter-peduncular space, 69. Inter-vertebral substance, 142. Intestinal tube, 166. Intuinesce.itia gaugliformis. 23. Iris, 62. Ischio-rectal fossa, 185. Island of Reil, 70. Isthmus faucium, 48. Iter ad'infundibulum, 75. a tertio ad quartum ventriculum, 75, 76. Jejunum, 167. Joint, ankle, 233. elbow, 143. hip, 230. lower jaw, 40. knee, 231. shoulder, 143. wrist, 144. Kidneys, 175. fcetal, 237. pelvis of, 175. Labia, majora, 201. minora, 202. Labyrinth, 81. membranous, 83. Lachrymal canal, 5. duct, 51. gland, 6. puuctum, 5. Lacteals, 168. Lacuna magna, 199. Lamina, cinerea, 70. cribrosa, 61. spiralis, 83. Large iutestine, 167. Larynx, 53. nerves of, 55. arteries of, 55. Lateral tract. 69. ventricles, 72. Lens, crystalline, 63. suspensory ligament of, 63. Lenticular ganglion, 21. Lieberkuhn, follicles of, 168. Ligameuta brevia of the fingers, 138. of the toes. 227. Ligaments, acromioclavicular, 143. alar, 232. ankle of the, 233. annular anterior of ankle, 219 external, 225. internal, 225. wrist, anterior of the, 137 posterior of the, 133 anterior of knee, 232. arcuatum externum, 177. internum, 177. astrngalo-scaphoid, 234. atlo-axoid', 59. bladder of the, 189. broad of the liver, 155. of the ut. rus. 189,203. breve plant®, 234. Ligaments, calcaneo astragaloid. 234. cuboid, 234. scaphoid, 234. capsular of the articular processes, 142. of the hip, 231. of the knee, 231. of the shoulder,143. of the thumb, 145. carpal, 145. carpo-metacarpal, 145. check, 59. chondro-sternal, 140. common anterior, 142. posterior, 142 coccyx of the, 229. conoid, 143. coraco-acromial, 143. clavicular, 143. humeral, 143. ' coronary, 171. of the knee, costoclavicular. 40. transverse. 141. vertebral, 140. xiphoid, 140. cotyloid, 231. crico-thyroid, 56. crucial, 60. of knee, 232. deltoid, 2*3. elbow of the. 144. fibula of the, 233. Gimbernat's, 180. gleuoid, 143. Hev's. 1^ hip-joint of the, 230. ilio-femoral, 231. lumbar, 229. interarticular of hip-joint, 231. of ribs, 141. interclavicular, 40. interosseous, fibula of the, 233. metacarpal bones, of the. 145. metatarsal bones. of the, 234. middle. 141. transverse, 141. interspinous, 142. intertransverse, 142. jaw, of the, 46. knee of the, 231. larynx of the. 55. lateral of the ankle, 233. of the elbow. 144. of the jaw, 46. of the knee, 231. of the phalanges, foot, 235. hand, 145. of the wrist, 144. liver, of the, 171. longuin planter. 234. lumho-sacral. 229. metatarsal, 234 INDEX. 247 Ligaments, mucous, 232. nucha?. 110. oblique, 144. obturator, 230. occiplto-atloid, 59. axoid, 59. odontoid, 59. orbicular, 144. ovary, of the, 204. palpebral, 5. patellae, 207, 232. pelvis, of the, 229. peroneo-tibial, 233. phalanges of the foot, 235. of the hand, 145. plantar, 234. posticum Winslowii, 232. Poupart's, 148. pterygo-maxillary, 47. pubic, 230. round, of the liver, 155. of the uterus, 203. sacro-coccygean, 229. sacro-iliac, 230. sacro-ischiatic, long, 230. short. 230. scapuloclavicular, 142. shoulder of the, 143. stellate, 141. sternal, 140. sternoclavicular, 40. stylo-hyoid, 37, 47. stylo-maxillary, 46. sub-flava, 142. sub-pubic, 230. supra-condyloid, 144. supra-spinous, 142. suspensorium penis. 147- tarsal, 234. tarso-metatarsal, 234. teres, 231. thyro-arytenoid, 55. thyro hyoid, 55. transverse of the crucial, 60. of the acetabu- lum, 231. of the atlas, 60. of the fingers, 124. of the knee, 232. of the metatar- sus, 234. of the scapula, 142. of the semilunar cartilages, 232. trapezoid, 143. triangular, 186. tympanum, of the, 81. uterus, broad of the, 189, 203. wrist, of the, 144. Ligamentum denticulatum, 118. nuchae, 110. Limbus luteus, 63. Linea alba, 147. arcuata, 148. Lineae transversee of fourth ventricle, (8. Lineae transversae of rectus muscle, 150 Liquor Cotunnii, 83. Scarpae, 83. Liver, 171. fcetal, 237. Lobes of the brain, 66. of the liver, 172. Lobule of the ear, 2. Lobus caudatus, 172. quadratus, 172. Spigelii, 172. Locus niger, 78. perforatus, 69. Lumbar fascia, ill. regions, 157. Lungs, 108. foetal, 238. Lymphatic glands of abdomen,'168 of axilla, 87. bronchial, 99. of elbow, 94. inguinal, 147, 179. mesenteric, 163. Lyra of the fornix, 73. Malleus, 80. Mammary gland, 86. Meatus auditorius, 3. of the urethra, female, 202. male, 198. Meatuses of the nares, 51. Meckel's ganglion, 50. Meconium, 237. Mediastinum anterior, 96. posterior, 104. testis, 200. Medullary substance of brain, 71. of cerebellum, 78. Medulla oblongata, 68. Meibomian glands, 5. Membrana dentata, 118. nictitans, 5. tympani, 79. secondary, 80 Membrane, choroid, 62. costocoracoid, 87. crico-thyroid, 66. hyaloid, 64. interosseous of fore-arm, 144 of leg, 233. obturator, 230. thyro-hyoid, 54. Membranous urethra, 198. labyrinth, 83. Mesenteric glands, 163. Mesentery, 158. Mesocolon, transverse, 158. Meso-csecum, 158. Meso-rectum, 158. Middle ear, 79. Mitral valve, 102. Modiolus, 83. Mons Veneris, 201. Morsus diaboli, 204. Muscles, abductor indicis^ 133. minimi digiti pedis, 226. 248 INDEX. Muscles, abductor minimi digiti manus, 135. pollicis pedis, 226. manus, 135. accelerator urinse, 186. accessorius, 227. ad sacro-lumbalem, 114. adductor brevis, 210. longus, 207. magnus, 210. minimi digiti manus, 136. pollicis pedis, 228. manus, 138. anconeus, 131. antitragicus, 3. arytenoideus, 54. attollens aurem, 2. attrahens aurem, 1. azygos uvulae, 49. basio-glossus, 52. biceps of the thigh. 215. of the arm, 90, 126, 144. biventer cervicis, 115. brachialis anticus, 91, 126. buccinator, 9. cerato-glossus, 52. cervicalis ascendens, 114. chondro-glossus, 52. ciliary, 62. coccygeus, 194. complexus, 115. compressor nasi, 8. sacculi laryngis, 54. urethrae, 193. constrictor isthmi faucium, 49. medius, 47. inferior. 47- superior, 47. vaginae, 187. coraco-brachialis, 90. corrugator supercilii, 4. cremaster, 149. crico-arytenoid lateralis, 54. posticus, 54. thyroideus, 54. cruraeus, 206. deltoid, 86. depressor anguli oris, 9. epiglottidis, 54. labii inferioris, 9. superioris alaeque nasi, 7 detrusor urinae, 195. diaphragm, 177. digastricus, 32. ear, of the, 1. erector clitoridis, 188. penis, 196. spinas, 114. extensor carpi radialis brevior, 130. longior, 130. ulnaris, 131. minimi digiti, 131. brevis digitorum, 219. communis digitorum, 130. Muscles, extensor longus digitorum, 219. indicis, 132. ossis metacarpi pollicis, 132. pollicis proprius, 219. primi internodii pollicis, 132. secundi internodii polli- cis, 132. flexor brevis digiti minimi, 136. pollicis, 135. carpi radialis, 125. ulnaris, 125. digitorum brevis, 226. profundus,129, 138-. sublimis, 126, 137. longus digitorum, 224, 227. pollicis, 129, 138. pedis, 224, 227. ossis metacarpi pollicis, 135. minimi digiti, 136. pollicis longus, 129. gastrocnemius, 222. gemellus, inferior, 214. superior, 214. genio-hyo-glossus, 53. genio-hyoid, 33. glosso-pharyngeus, 47. gluteus maximus. 211. medius, 212. minimus, 213. gracilis. 207. Guthrie's. 193. ^ helicis, major, 3. minor, 3. Hilton's, 54. Horner's, 6. hyo-glossus, 52. iliacus internus, 183. infracostales, 107- infra-spinatus, 122 intercostal, external, 107. internal, 107. interosseous, dorsal of the hand, 133. of the foot, 221. palmar, 139. plantar, 228. interspinals, 116. iniertransversales, 58,116. larynx of the, 54. latissimus dorsi, 110. laxator tympani, 81. levator anguli oris, 7. scapulae, 112. ani, 193. glandulse thyroideae, 30. labii superioris, 7- alaeque nasi, 6. inferioris, 9. INDEX. 249 Muscles, levator, palati, 49. palpebras, 19. levatores costaruin, 116. lingualis, inferior, 52. superior, 53. longissimus dorsi, 114. longus colli, 57. luinbricales of the foot, 227. of the hand, 137. massa carnea Jacobi Sylvii, 227. masseter, 12. internal, 35. multifidus spinas, 116. mylo-hyoid, 33. obliquus externus, 147. internus, 149. inferior, 20, 117. superior, 19, 117. obturator externus, 210. internus, 193, 214. occipito-frontalis, 3, 115. omo-hyoid, 27, 113. opponens minimi digiti, 136. pollicis, 135. orbicularis oris, 8. palpebrae, 4. palato-glossus, 49. pharyngeus, 49. palmaris brevis, 134. longus, 125. pectineus, 207. pectoralis major, 85. minor, 86. peroneus brevis, 224. longus, 224, 229. tertius, 220. plantaris, 222. platysma myoides, 25. popliteus, 224. pronator quadratus, 129. radii teres, 125. psoas magnus, 183. parvus, 183. pterygoid external, 34. internal, 35. pyramidalis of the abdomen, nasi. 4. pyriformis, 194, 213. quadratus femoris, 214. lumborum, 183. menti, 9. quadriceps extensor cruris, 207. rectus abdominiSj 150. capitis anticus major, 57. minor, 57- lateralis, 67. posticus major, minor. 117. femoris, 206. external, of the eye, 19. inferior, 19. internal, 19. superior, 19. sternalis, 150. retraheus aurem, 2. rhomboideus major, 111. Muscles, rhomboideus minor, 111. risorius Santorini, 9. sacro lumbalis, 114. salpingo-pharyngeus, 48. Sartorius, 206. scalenus anticus, 57. medius, 58. posticus, 58. semi-spinalis, 115. colli. 116. dorsi, 116. semi membranosus, 216. semi-tendinosus, 215. serratus magnus,'121. posticus inferior, 112. superior, 111 soleus, 222. sphincter ani, 185. internus, 186. vaginae, 187, 222. vesicae, 195. spinalis dorsi, 115. splenius, 112. capitis, 112. colli, 112. stapedius, 81. sterno-hyoid, 29. sterno mastoid, 27. sterno thyroid, 29. stylo-glossus. 37. stylo-hyoid, 33. stylo-pharyngeus, 37, 47. subclavius, 87. sub-cruraeus, 207: sub-occipital, lit. subscapularis, 121. supinator brevis, 132. longus, 126. supra-spinatus, 122. temporal, 13. tensor palati, 49. tarsi, 6. tympani, 81. vaginae femoris, 205. teres major, 122. minor, 123. thyro arytenoideus, 54. thyrohyoid, 29. tibialis anticus, 219. posticus, 224, 229. trachelo-mastoid, 114. tragicus, 3. transversalis of the abdomen, 149. colli, 114. pedis, 228. transverse of the ear. 3. transversus perinei, 186. alter, 186. profundus, 186. trapezius, 110. triangularis menti, 9. sterni, 95. triceps extensor cruris, 207 triceps extensor cubiti, 123. trochlearis, 19. ureters, of the, 196 250 INDEX. Muscles, vastus externus, 206. internus, 206. Wilson's, 193. zygomaticus major, 7. minor, 7. Musculi pectinati, 101. Nares, 51. Nasal fossae, 51. Nates of the brain, 76. Nerves, abdominal, 182. abducens, [c] 23, [o] 67- accessory, spinal, 68. acromial, 27. auditory, [cl 23, [o] 67. auricularis magnus, [o] 26, [d] 2. posterior, [c] 2. auriculo-temporal. [o] 35, [d] 11. brachial, 92. cardiac, 38. inferior, 44. middle, 39. superior, 39. cervical anterior, 26. posterior, 113. cervico-facial, 11. chorda tympani, 8, 36. circumflex, 93. clavicular, 27. coccygeal, 192. cochlear, [o] 23, [d] 84. communicans noni, 28. peronei, 217. poplitei, 217. cranial, [c] 20 [o] 66. crural, [o] 182, [d] 205. cutaneous, of the back, 113. external of arm, 92. of thigh, [o] 182, [d] 205, 215. internal, 92. lesser, 92. middle posterior, [o] 212, [c] 215. musculo, 92. plantar, 223. dental, inferior, [ol 35, [d] 9. superior, 23. descendens noni, [o] 34, [d] 28. digastric, 33. digital, of the foot, 218, 227. of the hand, 134, 137. dorsal, 113. dorsalis penis, [c] 185, [d] 197. eighth pair, [c] 23, [o] 68. facial, [c] 23, [d] 11, [o] 67. fifth pair, [cl 22, [ol 67. first pair, [c] 20, [o] 67. fourth pair, [c] 21, [o] 67. frontal, 22. gastric, 104. genito-crural, 182. glosso-pharyngeal, [cl 24, [d] 53. [o] 68. gluteal, [ol 192, [dl 213. gustatory, [o] 36, [dl 53. hypo-glossal, [o] 68, [c] 24, 38, [dl 53. Nerves, inferior maxillary, [o] 22, [d] 23. infra-orbital, [o] 22, [d] 7. intercostal, 106. intercosto-humeral, 92. interosseous anterior, [o] 127, [d] 129. posterior, [o] 93, [dj 131. Jacobsos's, 24. lachrymal, 22. larynx of, 55. laryngeal recurrent, [o} 41, 104, [d!55. superior, [o] 38, [d] 55. lumbar, 113. lumbo-sacral, 183, 192. malar, 11. masseteric, 35. maxillary inferior, 23. superior, 22. median, [o] 93, [e] 127, [d] 134, 137. molles, 39. motor oculi, [c] 21, [o] 67. muscular, superior, of the bra- chial plexus, 88. inferior, 88. musculo, cutaneous, of arm, 92. of leg, [ol 217, [d] 218, [c] 220. of thigh, [dl 150, [o] 182. musculo spiral, 93. mylo-hyoid, [o} 35, [d] 33. nasal, 22. naso-palatine, 50. ninth pair, [c] 24, [ol 68. obturator, [o] 183, 192, [d] 210, 215. occipitalis major, [o] 113, [dl 5. minor, [o] 26, [d] 2. oesophageal, 104. olfectory, [c] 20, [o] 67. ophthalmic, 22. optic, [cl 21, [o] 67. orbitar, 22. palatine, 50. perineal, cutaneous, [d] 185. peroneal, 217. petrosus superficialis major, 50. minor, 50. pharyngeal, 38. phrenic, [oj 41, [d] 96. plantar, external, 227. internal, 227. pneumogastric, [cl 24, 37, 41, [o] 68, [d] 104. popliteal, 217. portio dura, 23. mollis, 23. pterygoid, external, 36. internal, 36. pudic, internal, [d] 185, [o] pulmonary, 104. radial, [o] 127, [d] 130. recurrent, laryngeal, 104. INDEX. 251 Nerves, renal, 176. sacral, 113. sapheuous, external, [o] 217, [dl 218, [cl 221. long, 208. short, 208, 215. sciatic, [o] 192, [c] 213, [d] 216. lesser, [o] 192, [d] 212. scrotal, 182. second pair, [cl 21. [o] 67. seventh pair, [c] 23, [o] 67. sixth pair, [c] 23, [o] 67. spermatic, 201. spheno palatine, 36. spinal, 118. spiual accessory, [o] 68,119, [c] 24, 38, [dl 28. splanchnic, greater, 106. lesser. 106. stylo-hyoid, 33. sub-occipital, 58. subscapular, [o] 88, [d] 121. superficialis colli, 26. superior maxillary, [o] 22, [d]22. supra-orbital, [o] 22, [d] 4. scapular, [o] 88, [d] 113, 122. trochlear, 22. sympathetic, 39,105. prevertebral por- tion of, 105. vertebral portion of, 106. temporal, 11. temporo-facial, 11. third pair, [c] 21, [ol 67. thoracic, long, [o] 88, [d] 121. short, 88. tibial, anterior, [o] 217, [d] 218, [c] 220. posterior, [ol 217. [d] 223. trifacial, [cl 22, [o} 67. trochlearis, [c] 21, [o] 67. tympanic, 24. ulnar, [o] *G3, [c] 128, [d] 130, 134, 139. , vestibular, [o] 23, [d} 84. Vidian, 50. Wrisberg, 92. intermediate portion of, 67. Nose, cartilages of, 8. Nuck, canal of, 154. Nymphae, 202. (Esophagus, 105. Omentum, gastro-splenic, 158, 169. great, 157. lesser, 157. Openings in the diaphragm, 177. Optic commissure, 67. thalamus, 72, 76. tract, 67. Orbicular process, 81. Orbiculare, os, 81. Orbit, arteries of, 18. muscles of, 19. nerves of, 21. Os orbiculare, 81. Os uteri, 203. Os uteri, internum, 203. Otoconites, 83. Ovaries, 204. Pacchionian glands, 14. Pillars of diaphragm, 177. Palate, pillars of, 48. arches of, 48. soft, 48. Palmar arch, deep, 138. superficial, 136. Palpebral ligameuts, 5. Pancreas, 170. lesser, 170. Papillae of the tongue, 52. caliciform, 52. conical, 52. filiform, 52. fungiform, 52. kidney, 176. Parietes of abdomen, 146. Parotid gland, 11. Par vagum, 24. Peduncles of the cerebellum, 77. of the pineal gland, 76. Pelvis, viscera of, 188. Penis, 197. Pericardium, 97. Perineal centre, 186. Perineum, 185. Peritoneum, 157. reflections traced, 158. Pes anserinus of the face, 11. of the knee, 216. hippocampi, 73. Peyer's glands, 168. Pharynx, 46. Pia mater of the brain, 65. of the spinal cord, 118. Pillars of the palate, 48. of the abdominal ring, 148, 152. Pineal body, 76. Pinna, 2. Pituitary body, 17, 70. membrane, 51. Pleura, 104. Plexus aortic, 163. brachial, 45, 88. cardiac, 105. deep, 100. superficial, 100. carotid, 18. cavernous, 18. cervical, anterior, 26. posterior, 113. choroid, 72. hepatic, 174. hemorrhoidal, 189. hypogastric, 189. lumbar, 182. mesenteric, 162,163. ovarian, 189. prostatic, 189, 196. pterygoid, 37. pulmonary, 105. renal, 163. 252 INDEX. Plexus, sacral, 192. solar, 160. spermatic, 164, 201. splenic, 170. supra-renal, 175. uterine, 189. vaginal, 189. vesical, 189. Plica semilunaris, 5. Pomum Adanii, 55. Pons Tarini, 69. Varolii. 69. Popliteal space, 216. Portal vein, 159,160. Portio dura, 23. mollis, 23. Porus opticus, 63. Poupart's ligament, 148. Preperitoneal cavity, 151. Prepuce of the clitoris. 201. of the penis 197. Process orbicular. 8l. supracondyloid, 91. inferior vermiform, 77. superior vermiform, 77 Processus auditorius. 79. cochleariformis, 80. ad medullam. 77. ad pontem, 77. e cerebello ad testes. 76. vaginalis peritonei, 238. Promontory, 19. Prostate gland, 196. Prostatic urethra, 198. Pulmonary artery, 98. plexus, 104. sinus, 102. vein, 98. Punctum lacrymale. 5. Pylorus, 169. Pyramid, 80. Pyramids anterior, 6. Malpighi, of, 177. posterior, 69. Receptaculum chvli, 178. Rectum, 194. Regions, abdominal, 156. inguinal, 152. Reil. island of. 70. Rete pampiniforme, 201. Retina, 63. Rima glottidis, 55. Ring, abdominal, external, 148. internal, 153. crural, 180. Rivinian ducts, 52. Root of the lung, 99. Roots of the spinal nerves, 119. Rostrum, 70. Saccule, 83. Sacculus laryngis, 55. Saphenous opening, 179. Scala tympani. 83. vestibuli, 83. Scarpa, triaugle of. 208. Schneiderian membrane, 51. Sclerotic. 61. Scrotum^ 199. Semicircular canals, 82. Semilunar fold of Douglass, 151. valves, 102, 103. Septa of crural canal, 181. Septum of the auricles, 101. of the ventricles, 103. crurale, 180. lucidum. 73. nasi. 8. 51. of the tongue, 53 Sheath of the flexor tendons. 137. 226. of the pei:is. 198. of the rectus muscle, 151. Sigmoid flexure, 167. valves, 102. Sinuses of the aorta, 103. of the dura mater, 14. of the pulmonary artery. 102. of the uterus, 203. Sinus, basilar, 16. cavernous, 16. circular, 16. . coronary, 100. lateral. 1»>. longitudinal inferior. 14. superior. 14. occipital, 16. petrosal inferior, 16. superior, 16. pocularis, 198. prostatic, 198. straight, 14. transverse, 16. Valsalva, of, 103. Small intestines, 167. Soft palate, 48. Soemmering, foramen of, 63. Space, interpeduncular. 65. popliteal. 216. sub-arachnoid, 69. Speculum of Van Helmont, 177. Spermatic cord, 200. Spermatic fascia. 148.* Spheno-palatine ganglion, 50. Spinal arteries, 119. cord, 118. nerves. 118 veins, 119. Spleen, 169. supplementary. 170. Spongy portion of the urethra, 199. Stapes, 81. Steno's duct, 12. Stomach, 169. Structure of bladder, 195. cornea, 61. intestinal tube, 167. kidney, 176. liver, 174. lungs, 109. oesophagus, 105. ovaries, 204. parotid gland, 11. prostate, 196 spleen, 170. stomach, 169. INDEX. 253 Structure of testicle, 200. tongue, 51. trachea, 56. uterus, 203. vagina, 202. vesiculae seminales, 196. Striae longitudinales, 71. Sub-arachnoid space, 65,118. Sublingual gland, 52. Sub-maxillary gland, 33. Substautia perforata, 70. Superficial fascia of abdomen, 147. of thigh, 178. Supra-renal capsules, 174. :^uspensory ligament. f liver, 171. of penis, 147. Symphysis pubis, 230. Synovial membrauc of knee, 232. Ta?nia semicircularis, 72. hippocampi, 73. Tapetum oculi, 62. Tarsal cartilages. 5. Tendo, Achillis, 222. oculi, 5. Tendon, central of diaphragm, 177- Tentorium, 14. Testes, 199. cerebri, 76. descent of, 237. Thalamus opticus, 72, 75. Thoracic duct. 41. Thymus gland, 96. Thyro-hyoid membrane, 54. Thyroid axis, 43. cartilage, 55. body, 30. Tongue, 51. Tonsil, 48. Torcular Herophili, 14. Trabecules, 198. Trachea, 56. bifurcation of, 98. Tract, lateral, 69. optic, 67- Tragus, 2. Triangle of Hesselbach, 154. of Scarpa, 208. _ Triangles of the neck, 27. Triangular ligament, 186. Tricuspid valve, 101. Trigonum of the b.adder, 195. Trochlearis, 19. Tuber, cinereum, 70. Tubuli, galactophori, 86. lactiferi, 86. seminiferi, 200. uriuiferi, 176. Tunica, albuginea, 200. vaginalis, 199. Tympanic bone, 79. Tympanum, 79. Tyson's glands, 198. Umbilical region, 157. V radius, 195. Ureter, 175. Urethra, male, 198. Uretha, female, 202. Uterus, 202. Utricle, 83. Uvea, 62. Uvula of the bladder. 195. of the palate, 48. Vagina, 202. columns of the, 202. Vallecula, 77. Valsalva, sinuses of, 103. Valve, aortic, 103. .arachnoid, 78. coronary, 100. Eustachian, 100. ileo, cecal, 167. mitral, 102. pyloric, 169 semilunar, 102. sigmoid, 102. tricuspid, 101. veins of, 205. Vieussens, 76. Valvulae, conniventes, 168. Vasculum aberrans, 200. Vas deferens, 196, 200. Veins, axillary, 87. azygos major, 106! minor, 106. basilic, 90. cardiac, 100. cava, inferior, 97, 166. superior, 41, 97. cephalic, 90. internal, 37. coronary, 100. dorsalis penis, 197. facial, 10. femoral, 208. Galeni, 15, 74. gastric, 160. hemorrhoidal, 192. hepatic, 166. iliac, 165. innominata, 40, 96. jugular, anterior, 26. external, 25. internal, 37, 40. lumbar, 166. maxillary, internal, 37. median, 94. basilic, 94. cephalic, 94. mesenteric, inferior, 160. superior, 160. ovarian, 192. phrenic, 166. popliteal, 217. portal, 159, 160. profunda, 209. prostatic, 196. pulmonary, 98. radial, 94. renal, 166. saphenous, external, 218, 221. internal, 179, 205. spermatic, 164, 166, 192. splenic, 160. 254 INDEX. Veins, subclavian, 40. supra-renal, 166. Thebesii, 100. thyroid, 41. ulnar, 94. umbilical, 237. uterine, 203. vertebral, 40. Velum interpositum, 74. Venae Qaleni, 15, 74. Venesection, 93. Ventricle of the brain, fifth, 72.73. fourth, 71, 77. lateral, 71. third. 71, 74. Ventricles of the heart, 101,102. of the larynx, 55. Vermiform processes, 77. Vertebral aponeurosis, 112. Veru montanum, 198. Vesiculae seminales, 196. Vestibule. 82. Villi. 168. Vieussens, valve of, 76 Vincula subflava, 138. Vitreous humour, 64. Wharton's duct, 83. Whartonian gelatine, 236 Willis, circle of, 66. Wilson's muscle, 193. Wrisberg, nerve of, 92. Zonula ciliaris, 63 .^oS&^zyJU^ NATIONAL LIBRARY OF MEDICINE nlm 0320^514 3 11 I.1