ANTERIOR CERVICAL TRIANGLE. 1053 the arrangement of the cervical plexus will be seen, together with the origin of the phrenic nerve (p. 636); also the spinal-accessory nerve emerging from the substance of the sterno-mastoid muscle, and forming connections with the cervical plexus before it disappears beneath the trapezius muscle (p. 625). The seven cervical and first dorsal nerves are to be cleaned up to their emergence from the intervertebral foramina, the communicating branches of the sympathetic nerve being preserved if possible (p. 691); and the posterior thoracic nerve and the branch to the rhomboid muscles are to be found (p. 643). 4. Anterior Triangle and Deep parts of the Neck.-Let a dissection of the deep fascia and of the sterno-hyoid and sterno-thyroid muscles be made in the middle line between the larynx and sternum, to exhibit the relations of the trachea as connected with the operation of tracheotomy (p. 888), in particular noticing the position of the innominate artery, the common carotid arteries, the thyroid body, the inferior thyroid veins, and the arteria thyroidea ima, if it be present (pp. 340 and 920). The dissection of the anterior triangle of the neck is now to be proceeded with, by cleaning the whole of the sternomastoid, sterno-hyoid and sterno-thyroid muscles, and the anterior belly of the omo-hyoid muscle (p. 191); and in front of the sheath of the great vessels the descendens noni nerve, with its twigs to the three last named muscles, is to be laid bare (p. 626). Let the sheath of the vessels be opened, and the upper part of the common carotid artery exposed, with the pneumo-gastric nerve and internal jugular vein beside it; mark the place of its division into external and internal carotid arteries, and examine the first part of these two vessels, following the external carotid up to the parotid gland. Let the digastric and stylo-hyoid muscles be cleaned, and the parts be exposed in the submaxillary triangle, viz., the superficial part of the submaxillary gland, the submental branch of the facial artery, and the mylo-hyoid muscle, with the nerve that supplies it (pp. 183 and 608); observe also the ninth cranial or hypoglossal nerve lying close to the stylo-hyoid muscle, and dissect out its branch to the thyro-hyoid muscle (p. 627). The sterno-mastoid muscle is to be divided about three inches from its upper end, and the superior part is to dissected quite up to the bone, care being taken not to cut the spinal accessory nerve which pierces it. The sterno-hyoid and sterno-thyroid muscles ought now to be divided near their lower end, the thyroid body dissected, and its form and relations noted. The dissector will then direct his attention to the branches of the external carotid artery; he will dissect the superior thyroid artery and note its sterno-mastoid branch (already cut), and the hyoid, laryngeal, and crico-thyroid branches; he will dissect also the commencement of the ascending pharyngeal artery, the occipital artery as far as the occipital groove of the temporal bone, the posterior auricular artery, the lingual artery as far as the border of the hyoglossus muscle, and the facial artery as far as the lower jaw (p. 346); he will also lay bare the pneumo-gastric nerve as far as convenient, tracing the superior and external laryngeal branches (p. 622). In the lower part of the neck, the subclavian artery is now to be examined in the three parts of its course; and the different relations of the subclavian and common carotid arteries in the first part of their courses on the two sides of the body are to be carefully compared (p. 364). The internal jugular and the subclavian veins, with the branches entering them, are to be dissected, and on the left side the arched part of the thoracic duct descending into the angle of junction of these two veins (pp. 459, 469, and 488). The branches of the subclavian artery are to be displayed, viz., the ver tebral and internal mammary arteries, the thyroid axis, from which arise the inferior thyroid giving off the ascending cervical artery, the suprascapular artery, and most frequently the transverse cervical dividing into the superficial cervical and posterior scapular; lastly, there are the deep cervical and superior intercostal arteries coming off either as a single trunk or separately (p. 366). The frequent origin of the posterior scapular artery from the third part of the subclavian artery and other varieties will here require to be attended to (p. 372). The trunk of the sympathetic nerve is to be dissected, with its three cardiac and its other branches, as high as the first cervical nerve (p. 688); and the recurrent laryngeal branch of the vagus nerve is to be found between the gullet and trachea, and traced up to the larynx (p. 622). 5. Superficial Dissection of the Face.-In proceeding with this region, the dissectors ought to expose in concert the superficial muscles of the face on one side, keeping only the principal blood-vessels and nerves. They ought likewise to make a more detailed exposure and dissection of these vessels and nerves on the other side, for which purpose the superficial muscles must be in some measure sacrificed. If this method cannot be followed in concert, each dissector must display as much as possible all the parts on his own side, in which case he will do best to begin with the superficial muscles. To exhibit the superficial muscles of the face, the skin is to be reflected from the middle line, from which one or two such transverse incisions as shall seem necessary are to be directed outwards. It is most convenient to begin with the orbicularis palpebrarum muscle, removing the skin from the circumference to the margin of the eyelids, and dividing it along these margins (p. 171). The muscles between the eye, nose and upper lip may then be exposed, the principal of which are these :-the compressor naris, the levator labii superioris alæque nasi, the levator proprius labii superioris, and the zygomatici, more deeply the corrugator supercilii, the levator anguli oris, the pyramidalis nasi continued from the frontalis, the dilatator naris, &c. Below the mouth the depressor anguli oris and depressor labii inferioris will be seen. A more complete view of the orbicularis oris may be obtained by dissecting it from the inner aspect of the lips; and the levator menti is best displayed by making an incision down to the bone in the middle line, and dissecting outwards. To expose the nerves and blood-vessels of the face, the skin may be reflected as stated above from the middle line outwards. The surface of the parotid gland is to be cleaned, and search made for the branches of the facial nerve as they emerge from underneath its upper and anterior margins (p. 614). The duct of the parotid gland, and the transverse facial artery are also to be dissected (p. 354). The branches of the facial nerve are to be followed forward, and, as far as possible, their connections with the infraorbital, buccal and inferior labial branches of the fifth nerve are to be traced. Let the dissector cut the superior attachment of the levator proprius labii superioris muscle, and dissecting down upon the infraorbital foramen, follow out the distribution of the infraorbital nerve and artery emerging from it (pp. 602 and 357). Let him also cut carefully down upon the mental foramen, and follow out the inferior labial nerve and artery emerging thence (p. 608). The facial artery and vein with their branches are to be dissected out from the point to which they have been previously traced at the border of the jaw. The principal branches of the artery, such as the inferior labial, SUPERFICIAL AND DEEP DISSECTION OF THE FACE. 1055 the superior and inferior coronary, the lateral nasal and the angular, are to be exposed (p. 350). The branches of the facial nerve should be traced backwards through the parotid gland to the emergence of the main trunk from the stylomastoid foramen while this is being done, the connections of this nerve with the auriculo-temporal branch of the fifth and with the great auricular nerve will be preserved, and the twigs to the posterior belly of the digastric muscle and the stylo-hyoid muscle should be sought for, close to the skull (p. 613). The continuation of the external carotid artery into the superficial temporal will be seen; and in dissecting out the remains of the parotid gland, the position and relations of that gland can be studied (p. 814). In this part of the dissection the student should also observe the connections of the part of the cervical fascia which separates the parotid and submaxillary glands, and which is continuous with the strong band known as the stylo-maxillary ligament (p. 197). Finally, the dissector may clean and examine the tarsal and nasal cartilages (pp. 706 and 771). 6. Deep Dissection of the Face.-The masseter muscle, and the nerve and artery which enter its deep surface from the sigmoid notch of the lower jaw are to be examined (p. 181), and the temporal fascia removed, the orbital twig of the superior maxillary nerve being sought between its layers (p. 600). By means of the saw and bone-nippers, the zygomatic arch may then be divided in front and behind in such a manner as exactly to include the origin of the masseter muscle, which should be turned downwards and backwards, the masseteric nerve and artery being in the meantime preserved. Let the coronoid process be divided by a vertical and horizontal incision with the saw and nippers as low down as possible, care being taken not to cut the buccal nerve, which lies in close contact with the temporal muscle. The coronoid process with the temporal muscle attached is to be reflected upwards, and the neck of the jaw is to be divided a little below the condyle, and as much of the ramus of the jaw is to be removed as can be cut away without injury to the inferior dental artery and nerve which enter the foramen. The internal maxillary artery with its branches is to be exposed as far as can be done without injury to the external pterygoid muscle, on whose outer surface it generally lies; it is frequently, however, covered by it. The gustatory and inferior dental nerves will be seen below the inferior border of the external pterygoid muscle, the latter nerve giving off the mylo-hyoid branch before entering the inferior dental canal, and resting on the fibrous slip commonly known as the internal lateral ligament of the jaw, between which and the jaw the internal maxillary artery likewise passes. Above the superior border of the same muscle will be seen the anterior and posterior deep temporal arteries and nerves, and between the two parts of the same muscle, the buccal nerve and vessels. After the external pterygoid muscle has been examined (p. 182), the temporo-maxillary articulation is to be studied (p. 132), and opened by cutting the external lateral ligament and dividing the capsule of the joint above and below the interarticular fibro-cartilage, and the condyle of the jaw is to be disarticulated; care being taken not to cut the auriculo-temporal division of the inferior maxillary nerve, which is in close contact with the inner side of the capsule (p. 606). The external pterygoid muscle may now be turned forward along with the head of the jaw, and its nerve found; after which it may be removed. The branches of the internal maxillary artery in the vicinity of the pterygoid muscles are thus brought fully into view, viz.: in the first part of its course, the inferior dental, the middle meningeal giving off the small meningeal artery, the two deep temporal, the pterygoid and other muscular branches next, more deeply within the pterygoid muscles, the posterior superior dental and the infraorbital branches (p. 354). The chorda tympani nerve is to be dissected upwards to the fissure of Glaser, from its point of junction with the gustatory nerve under cover of the external pterygoid muscle, and the branches of the inferior maxillary nerve are to be traced back to the foramen ovale (p. 605): the auriculo-temporal nerve will frequently be found embracing the middle meningeal artery. The internal pterygoid muscle is to be examined as far as it can be laid bare (p. 181). The auriculo-temporal division of the inferior maxillary nerve is then to be traced to its distribution, and the pinna of the ear is to be dissected so as to show the form and extent of its cartilage, the small muscles on its surface, and the final distribution of its nerves (p. 741). 7. The Orbit. The dissection of the orbit and the parts passing into it may next be proceeded with. Let a vertical cut be made with the saw through the frontal bone, near the inner angle of the orbit, immediately above the fovea trochlearis; and another from above the ear, downwards and forwards, through the lateral wall of the skull, towards the sphenoidal fissure. Remove the outer part of the malar bone with the bone-nippers, separate carefully with the handle of the knife the periosteum and contents of the orbit from the upper and outer walls, and unite the inner saw-cut with the sphenoidal fissure, immediately outside the optic foramen, by means of the chisel; then, with the bone-nippers, remove the isolated piece of bone so as to unroof the orbit, and afterwards divide the periosteum longitudinally, and reflect it. On the upper surface of the contents of the orbit posteriorly is the fourth nerve, which is to be traced forwards from the cavernous sinus where it enters the orbital surface of the trochlearis muscle, and that muscle is to be displayed (pp. 594 and 179). The frontal nerve, occupying the middle of the space, is to be traced back to its origin from the ophthalmic division of the fifth nerve (p. 597). The lachrymal gland is to be exposed (p. 709); and from its posterior border the lachrymal nerve is to be traced back to its origin from the ophthalmic nerve, while at the same time its malar branch and palpebral distribution may also be seen. The levator palpebræ muscle, and the inferior, external and internal recti muscles are to be displayed (p. 179), and the ocular surface of each cleared; when the sixth nerve will be seen ending in the external rectus, and branches of the third in the other three recti muscles. These nerves are now to be traced backwards between the two heads of origin of the external rectus muscle to the cavernous sinus (pp. 593 and 610). Below the superior rectus muscle the nasal nerve, derived from the ophthalmic, will be seen crossing the optic nerve; it will be followed to the anterior internal orbital foramen, and its infratrochlear branch traced to the lower eyelid; it is then to be dissected back to its origin, and the long and delicate root of the lenticular ganglion sought for on the outer side of the optic nerve. The ophthalmic or lenticular ganglion is on the outside of the optic nerve, and may be most easily found by tracing the short and thick twig which runs into it from the inferior division of the third nerve. In front of the ganglion its ciliary branches may be seen (p. 599). The remainder of the fat is to be removed from the lower part of the orbit; the distribution of the ophthalmic artery is to be displayed (p. 360); and the lower division of the third nerve is to be traced forwards to the inferior rectus and obliquus muscles. By a slight dissection from the front DEEP DISSECTION OF THE FACE. 1057 of the orbit the insertions of these muscles may be more fully displayed. The contents of the orbit may be afterwards divided behind and turned forward, to admit of the tensor tarsi muscle and the lachrymal sac being dissected. Finally, if the subject be favourable, the nasal nerve may be traced through the ethmoid bone to its distribution in the interior of the nares, and its external twig to the tip of the nose examined. 8. Deep view of the Fifth Nerve. Spheno-palatine and Otic Ganglia. Internal Ear.-After the dissection of the orbit has been completed, the foramen rotundum and infraorbital canal are to be laid open, and the superior maxillary nerve and its orbital and dental branches dissected (p. 600). Remove with the saw a further portion of the skull towards the meatus externus, reaching as far as the foramen spinosum, and with the chisel or nippers cut down close to the foramen ovale ; remove also a portion of the bone above the pterygoid processes so as to open up the spheno-maxillary fossa, and the spheno-palatine ganglion will be brought into view. The connection of the ganglion with the superior maxillary nerve may then be made out. Trace the nasal and naso-palatine branches of the ganglion through the spheno-palatine foramen, and the palatine branches passing downwards. Lay open the Vidian canal and dissect the Vidian nerve back to the great superficial petrosal nerve (p. 603). At the same time the infraorbital, spheno-palatine, descending palatine and Vidian branches of the internal maxillary artery will be noted (p. 356). The otic ganglion may also be in part seen by breaking open the foramen ovale, following upwards the nerve of the internal pterygoid muscle, and slightly everting the trunk of the inferior maxillary nerve (p. 608). The twigs from this ganglion to the tensor palati and tensor tympani muscles may be found. The otic ganglion, however, can only be seen to advantage in dissections made from the inner side of the internal pterygoid muscle and inferior maxillary nerve. The Eustachian tube may be laid bare in the posterior part of its course, and may be opened, and the attachment of the tensor tympani above it shown (p. 747). By now sawing the wall of the skull down to the margin of the external auditory meatus, and removing with the bone-nippers, cautiously, the anterior wall of the meatus externus, the membrana tympani may be exposed ; and by unroofing the tympanic cavity in continuation of the Eustachian tube backwards, the malleus, incus and stapes, as well as the tendon of the tensor tympani muscle will be brought into view (p. 748). The mode of action of the latter on the membrana tympani may be studied; also the chorda tympani nerve will be seen traversing the cavity. The malleus and incus are to be carefully removed; then, placing one point of the bonenippers in the internal auditory meatus, lay open with the other the vestibule and cochlea, and let the relation of the portio mollis and portio dura nerves to these cavities be observed (pp. 610 and 615). The manner in which the stapes fits into the fenestra ovalis may now be seen to advantage, the tendon of the stapedius muscle requiring, however, to be cut across before that ossicle can be removed. With the aid of the bone-nippers, the fleshy part of the stapedius may be laid bare, descending in the mastoid part of the temporal bone, close to the facial nerve; and, in favourable circumstances, the corda tympani may be traced back to the facial nerve. 9. Submaxillary and Sublingual Regions.-Let the lower jaw be divided in front of the masseter muscle, and let the gustatory and mylo-hyoid uerves be followed from the pterygoid into the submaxillary region. The |