between the stylo-glossus, with which its fibres intermix, and the lingualis.

The LINGUAL ARTERY, Fig. 65 (s), enters the submaxillary region a short distance outside the free extremity of the great cornu of the hyoid bone, and on a plane somewhat deeper. It almost immediately passes behind the hyo-glossus muscle, just above the cornu of the hyoid bone, to get between the genio-hyo-glossus and lingualis. The middle constrictor of the pharynx lies behind it, in the first part of its course. The situation and relations of this artery should be noticed with reference to the application of a ligature to it.

The STYLO-PHARYNGEUS MUSCLE, Fig. 70 (4), arises from the styloid process, passes downwards and inwards to the pharynx, which it enters between the superior and middle constrictors. The glosso-pharyngeal nerve runs along the side of this muscle between it and the stylo-glossus to the margin of the hyo-glossus, beneath which it passes to the base of the tongue, sending filaments in this region to the pharyngeal plexus. The dissector will find the stylo-pharyngeus muscle a guide for finding this nerve.

The SUBLINGUAL GLAND, Fig. 3 (5), is the smallest of the three large salivary glands. It is situated near the symphysis of the chin, occupying a fossa on the inner side of the lower jaw. Its upper surface is covered by the mucous membrane of the mouth, between the incisor teeth and the tongue; below, it rests upon the mylo-hyoideus muscle; anteriorly, it is in relation with the lower jaw. It is sometimes connected by a process with the submaxillary gland. Its excretory ducts are ten or twelve in number. They open into the mouth near the frænum of the tongue. Sometimes they are called the ducts of Rivinus. A communication occasionally exists between these ducts and the duct of Wharton.

The relations of the submaxillary and sublingual glands are worthy of particular notice. It will be observed that the submaxillary is covered externally by skin, superficial fascia, platysma myoides, and deep fascia, while the sublingual is covered internally by mucous membrane, and submucous areolar tissue. The mylo-hyoideus forms the principal septum between them. They are both in apposition with the lower jaw; the sublingual occupying the sublingual fossa,

and the submaxillary the submaxillary fossa, while the two fossæ are separated by the mylo-hyoid ridge.

In dissecting the upper part of the superior carotid region, the first thing which should be sought is the hypoglossal nerve. This enters it beneath the posterior belly of the digastricus, at a point almost directly below the angle of the lower jaw, passes downwards, forwards, and upwards, to enter the submaxillary region near the free end of the great cornu of the hyoid bone. It thus forms a curve in this region, the convexity of which looks downwards. The lowest part of this curve is about three-fourths of an inch below the digastricus. As it descends beneath the digastricus, it gives off the descendens noni.

The DESCENDENS NONI, Fig. 67, (4, 5), passes vertically downwards, receiving one or two branches from the second cervical nerve, or cervical plexus, by which a loop is formed; from the convexity of this loop, filaments are sent to the omohyoideus and sterno-hyoideus and thyroideus. The apparent origin of this varies in different subjects. Sometimes it seems to come from the pneumogastric, occupying, in this case, for a short distance, the groove behind and between the common carotid and internal jugular vein; again, it will be found leaving the hypoglossal high up in the parotid region.

If there be any difficulty in finding the nerve in the upper part of this region, it is better either to find one of its branches and trace it upwards, or to trace the hypoglossal nerve itself up into the parotid region. In this way the student will be certain to find it. The descendens noni usually, near its commencement, winds round the occipital artery. As this nerve lies on the sheath of the common carotid, it is liable to be injured in ligating that artery.

The SPINAL ACCESSORY NERVE passes through the upper and posterior part of this region, to perforate the sterno-cleidomastoideus. It is is most readily found by carefully dissecting the inner and posterior surface of that muscle, and looking for the nerve as it enters it. Occasionally, the nerve passes beneath the muscle.

The superior laryngeal branch of the pneumogastric may be found with the laryngeal branch of the superior thyroid artery, between the hyoid bone and the thyroid cartilage. They pass beneath the thyro-hyoid muscle, to perforate the thyro

hyoid membrane. This nerve can be exposed more conveniently at another stage of the dissection of the neck. Having found this portion of it, the student may avoid destroying it as he proceeds.

As the lower part of the inferior carotid region has already been dissected, the student will have no difficulty in tracing the arteries in its upper part. The common carotid usually bifurcates at a point nearly opposite to the superior border of the thyroid cartilage. The external is at first more internal than the internal carotid itself. It gives off the following branches before passing beneath the digastricus:

The SUPERIOR THYROID, Fig. 65 (4), arises near the bifurcation, passes inwards, forwards, and downwards, beneath the omo-hyoideus and sterno-thyroideus, to be distributed to the upper and anterior portion of the thyroid gland. It usually gives off the laryngeal branch, which goes to the thyro-hyoid space to enter the larynx; the cricoid branch, which rests on the anterior crico-thyroid ligament; a branch to the sternocleido-mastoideus; and branches to the muscles with which it is connected. This artery is quite superficial in its course. The lingual arises just above the preceding, and passes upwards and inwards to enter the submaxillary region. It is deep-seated in its whole course.

The facial artery comes off just below the digastric muscle, and goes up into the submaxillary region.

The inferior or ascending pharyngeal arises near the bifurcation and from the deep part of the artery, and goes upwards to the jugular foramen, through which it enters the cavity of the cranium, sending branches, as it ascends, to the pharynx and soft palate.

The OCCIPITAL, Fig. 65 (13), arises from the posterior part of the artery, passes upwards and backwards, at first behind the digastricus, and then more horizontally beneath the sternocleido-mastoideus, trachelo-mastoideus, and splenius capitis, to reach the occiput. It emerges beneath the integument and fascia, just outside the cranial origin of the trapezius. It gives off branches to the muscles along its course, and, just before it ascends on the occiput, it sends downwards quite a large branch, called the arteria princeps cervicis; this branch descends on the back of the neck, and anastomoses with the transverse humeral. The occipital artery ramifies on the back of the head, beneath the skin.

The POSTERIOR AURICULAR, Fig. 65 (16), arises above, or in common with, the occipital, and passes upwards and backwards between the mastoid process and meatus auditorius. It ramifies on the external ear, and beneath the integument behind the ear.

The styloid is more frequently a branch of the posterior auricular; it enters the foramen stylo-mastoideum, and goes to the middle ear.

Besides the branches just mentioned, the external carotid generally sends two or three small ones to the sterno-cleidomastoideus.

SECT. II. DISSECTION OF THE DEEP PARTS OF THE NECK.

The examination of these parts requires a displacement of the lower jaw, or at least the half on the side upon which they are to be dissected. The only additional section which will be required will be through the symphysis of the chin, when the remaining portions of the jaw upon that side may be drawn upwards and forwards, out of the way, or they may be entirely removed.

The parts to be examined in the present dissection are the internal carotid artery, the internal jugular vein, the pneumogastric, the glosso-pharyngeal, the spinal accessory, the hypoglossal, and the sympathetic nerves, and the pharyngeal plexus, and some of the deep muscles of the neck. Most of the parts just enumerated have been examined as they were found in the different regions already dissected. The following description, therefore, will be confined principally to those portions of them which remain to be exposed.

The branches of the external carotid may be cut away, as the dissector shall find it necessary, in the progress of the dissection. The digastricus and the stylo-hyoideus may be divided near their hyoid attachments, and reflected backwards.

The INTERNAL CAROTID, Fig. 65 (2), passes upwards nearly in a vertical direction from the bifurcation of the common carotid, to the foramen caroticum in the petrous portion of the temporal bone, through which it enters the cranial cavity. In the superior carotid region, it is quite superficial, being covered merely by the integument, platysma myoides, and

the superficial and deep fascia; but, as it ascends, it gradually becomes deeper seated. Its size is not varied in this part of its course.

Below the digastricus, the hypoglossal nerve and the occipital artery cross it in front, while the external carotid lies on the inner side of it. Above the digastricus, and in the parotid region, it is crossed in front by the glosso-pharyngeal nerve and the stylo-glossus and stylo-pharyngeus muscles, Fig. 67, which pass between it and the external carotid. It is also covered by the parotid gland, in which it is sometimes partially lodged.

On its inner side are the pharynx and sympathetic nerve. Externally it is in relation with the internal jugular, the pneumogastric, the hypoglossal, and glosso-pharyngeal nerves. These nerves at first lie behind it, but soon get on the outside between it and the vein. The two latter, however, do not continue in this connection down to the common carotid, but cross over in front of the artery, the one above, and the other below the digastricus, as before mentioned.

Behind, it rests on the rectus capitis anticus major, separated from it by fascia and by the pharyngeal and superior laryngeal branches of the pneumogastric, which pass inwards beneath it.

The inferior or ascending pharyngeal artery runs at first on the inner side of the internal carotid, then behind it, up to the foramen lacerum posterius, or jugular foramen. The internal carotid is surrounded by a plexus of nerves.

The relation of this artery to the pharynx is worthy of notice. It sustains nearly the same relation to the internal surface of the pharynx, as regards the intermediate structures, that it does to the external surface of the neck in the superior carotid region.

The INTERNAL JUGULAR VEIN, Fig. 67 (27), commences at the foramen lacerum posterius, and terminates by uniting with the subclavian to form the vena innominata. Near the foramen it is removed a short distance from the internal carotid, the intermediate space being occupied by nerves. There is also a small space between it and the common carotid in the lower part of the neck. This vein is a continuation of the lateral sinus; it increases in size as it receives collateral branches in its course down the neck. It