then passes through this foramen to the mucous membrane of the hard palate, just behind the incisor teeth.

A VIEW OF THE FIRST PAIR OR OLFACTORY NERVES, WITH THE NASAL BRANCHES OF THE FIFTH PAIR.-1. Frontal sinus. 2. Sphenoidal sinus. 3. Hard palate. 4. Bulb of the olfactory nerve. 5. Branches of the olfactory nerve on the superior and middle turbinated bones. 6. Spheno-palatine nerves from the second branch of the fifth pair. 7. Internal nasal nerve from the first branch of the fifth. 8. Branches of 7 to the Schneiderian membrane. 9. Ganglion of Cloquet in the foramen incisivum. 10. Anastomosis of the branches of the fifth pair on the inferior turbinated bone.

These nerves ramify between the mucous membrane and periosteum. To obtain a distinct view of them, the part should be kept for some time in dilute nitric acid; when, by separating the membrane from the bone, they can be seen from the fibrous surface.

The anterior palatine nerve gives off a branch which enters the nasal fossa near the posterior extremity of the inferior turbinated bone, and ramifies in the lower part of the fossa.

The internal nasal branch, Fig. 52 (7), of the ophthalmic, enters the nasal cavity through the anterior part of the ethmoid, near the crista galli, sends some twigs to the septum and outer wall, and then passes down on the inner surface of the nasal bone to its junction with the lateral cartilages of the nose, where it perforates the fibrous structure connecting the cartilage and bone, and is distributed to the integument covering the nose. In its course, some filaments penetrate the bone. The arteries entering the nasal fossa consist of branches from the spheno-palatine, the infra-orbital, the palatine, the

pterygo-palatine, the supra-orbital, the ethmoidal, and the facial. From these various sources the mucous membrane of the nasal fossa is abundantly supplied with arterial blood.

The veins, Fig. 8, k, correspond with the arteries. Some branches find their way into the frontal sinus, and through the foramen cæcum communicate with the superior longitudinal sinus of the dura mater.

The student should study the nasal fossæ with reference to plugging the nares to arrest hemorrhage; the removal of polypi, and foreign bodies which may happen to be lodged in them; the introduction of instruments to reach the Eustachian tube, or to be conducted into the pharynx through the nasal cavity; their proximity to the brain and its meninges; and their connection with the sphenoidal, frontal, and maxillary sinuses, Fig. 52 (1, 2), and the ductus ad nasum. The exact relation of the osseous sinuses, just mentioned, to the nasal fossæ should be carefully noted; the manner in which a purulent collection in either of these sinuses would be affected, in regard to its escape, by the position of the head.

If, for instance, pus should be formed in the maxillary sinus or antrum, a large proportion of it would necessarily be retained as long as the head was kept in a vertical position, on account of the opening from it into the middle meatus being situated in the upper part of its nasal wall; nor could it be emptied of its contents until the head was placed upon the opposite side. In case of a purulent discharge from the nose, a knowledge of this fact would enable the physician to determine whether it came from the antrum or not.

The contents of the sphenoidal sinus, in case of a purulent collection, would be emptied entirely only when the head was placed with the face looking directly downwards. As the opening from the frontal sinus is in its floor, its contents would escape when the head occupied a vertical position. The nasal orifice of the ductus ad nasum should be observed, and the introduction of a probe of the proper curve into it should be practised upon the subject. The same thing should be done with the antrum and Eustachian tube.

A correct idea of the dimensions of the nasal fossa is exceedingly important. It will be observed that the upper part of it is very narrow, and will not admit an instrument of much size without injuring the parietes.

The walls of the antrum, Fig. 51 (14), should be noticed as

regards their thickness, and their relation to the mouth, the nose, the orbit, the pterygo-maxillary fossa, and the face.

The frontal sinus also demands attention, with reference to diagnosis, in diseases and injuries of it, and the proper treatment to be instituted, whether medical or surgical.

Before dissecting the tongue, soft palate, pharynx, and larynx, the student should carefully examine the topography of the mouth, the fauces, and the pharynx. For this purpose, the head must be divided vertically, a little to one side of the median line, so as to avoid injuring the septum of the nose, as before directed, and at the same time leave the uvula entire. The back of the neck should be dissected before this section is made, in order that the upper cervical vertebræ may be divided with the head. It will not be necessary to divide the tongue or the larynx. The pharynx, however, should be opened along the median line posteriorly.

SECT. XI.-TOPOGRAPHY OF THE MOUTH, FAUCES, AND PHARYNX.

The MOUTH is the first division of the alimentary canal. It is exceedingly important, on account of the several functions with which it is associated. The organ of taste is located here; the processes of mastication, insalivation, the articulation of sounds, and the commencement of deglutition, all take place in the cavity of the mouth. It is surrounded by movable walls, except the upper, and consequently is subject to great variation in its dimensions. When the lower jaw is applied to the upper, it is divided into two cavities; the outer one is situated between the cheeks and lips, and the teeth and alveolar processes; the inner one is embraced within the circumference of the teeth and alveoli. The former receives the saliva secreted by the parotid glands; while that secreted by the submaxillary and sublingual is poured into the latter, thus securing a proper intermixture of the saliva with the food. The external orifice of the mouth opens into the one, and the internal orifice opens out of the other into the fauces. The food is kept between the teeth until properly masticated, by the action of the lips and cheeks on the outside, and the

tongue on the inside of them. The lips are active agents in receiving food into the mouth, and the tongue is concerned in forcing it back into the pharynx.

Both cavities are lined by mucous membrane, which is worthy of particular attention, as presented on the upper surface of the tongue, on the alveoli and hard palate, and in the other parts of the mouth.

The LIPS are composed of the following structures: The orbicularis oris forms the middle and larger portion of their bulk; it is covered on the outside by skin and subcutaneous areolar tissue; and, on the inside, by mucous membrane and submucous areolar tissue. They are abundantly supplied with arteries and nerves. The labial glands are situated on their inner side. The lips never contain adipose tissue. Their great size in the African is owing mainly to the size

of the orbicular muscle.

The free borders of the lips in a state of health are of a bright red color; but in an anæmic condition of the system, or when the blood recedes from the cutaneous capillaries, they present a pale appearance. The study of the lips is very interesting and important to the artist, as they have so much to do in giving expression to the countenance.

The CHEEKS are composed of the same elements as the lips; besides, they usually contain more or less adipose substance. The principal muscle in each cheek is the buccinator. It is perforated opposite the second upper molar tooth by the duct of the parotid. Besides the small buccal glands beneath the mucous membrane, there are two quite large ones situated between the masseter and buccinator muscles; these are called the molar glands.

The fulness or plumpness of the cheeks depends partly on the fat which they contain, and partly on the presence of the teeth. The mucous membrane of the lips and cheeks is reflected upon the alveolar processes, where it is blended with the fibrous structure beneath. It is here thick and dense, and possesses very little sensibility, as shown in infants, and in old people who have lost their teeth. It connects on the two sides of the alveolus, between the teeth and over the interalveolar septa. The gums are supplied with mucous follicles. Tartar, as it is called, is a product of these follicles.

The mucous membrane forms a fold on the inner side of each lip, which is called frænum labii.

In the posterior division of the buccal cavity, the mucous membrane and the papillae of the tongue are the principal things now to be examined. The portion covering the hard palate is similar to that of the gums. It is rough and uneven. Between it and the bone ramify vessels and nerves. It covers over and conceals the anterior and posterior palatine foramina. Between the alveolar processes of the lower jaw and the free border of the tongue it is thin, and loosely connected to the subjacent tissues. In the median line and on the under surface of the tongue it presents a fold, called the frænum lingua. This is so large and unyielding in some cases, that it interferes with the movements of the tongue. The difficulty is removed by dividing its free border. Just behind the incisor teeth, Fig. 53 (3), the mucous membrane is perforated

A VIEW OF THE LOWER JAW, WITH THE TONGUE DRAWN UPWARDS, SO AS TO SHOW ITS UNDER SURFACE IN SITU.-1, 2. The posterior superior surface of the tongue, with the papillæ maximæ. 3. The opening of the duct of the submaxillary gland, or the duct of Wharton. 4. The sublingual gland, seen under the mucous membrane of the mouth. 5. The lower jaw.

by the excretory ducts of the sublingual and submaxillary glands. The upper surface of the tongue is studded with papillæ, Fig. 54, which render it quite rough. There are two kinds of these papillæ. One set is perforated, and the other is not. The former are situated near the base of the