latter in the plane of the posterior choanæ with a similar rolled end. In the living, no structure above the middle turbinal can be recognized. Dissection, however, shows one well-defined, though smaller, turbinal process above the middle concha, and above this usually at least one, sometimes two, smaller bony turbinal folds. All these structures are lined with mucous membrane.

The narrow chink between the nasal septum and the

FIG. 6. Frontal section through the ing the anterior surface of the sphenoid. is had of the nasopharynx: O, Roof; a, b, b, depression between the anterior and posterior folds of the upper nasal wall; c, c, anterior fold, d, posterior fold, of the upper nasal wall; e, spheno-ethmoid recess; forifice of sphenoid sinus; t, Eustachian prominence; p, p, pharyngeal tonsil (Zuckerkandl).

turbinal surfaces above the middle turbinal is the olfactory fissure in which the nerves of smell spread out in the mucous membrane. Between the middle and the upper turbinals and the external wall of the nasal cavity are the ethmoid cells, the spaces confined by the deviated and partially coalesced turbinal processes and accessory septa. These are a series of more or less communicating cells lined by mucous membrane with orifices into the nasal passage (see ¶ 43). Beneath the front end of the

middle turbinal are the openings leading into the frontal and maxillary sinuses. The sphenoid sinus communicates with the nasal space through a slit in the anterior sphenoid wall. The only other channel connected with the nose is the lacrimal duct, which empties under the external side of the inferior turbinal, close to its front end.

The nasal passages connect with the pharynx through the posterior choanæ. These openings, each of oval shape, are separated by the posterior border of the vomer, and are bounded above by the lower surface of the sphenoid; externally and below, by the palate bones. Their plane is not quite vertical, but slants slightly downward and forward (Fig. 6).

6. The pharynx may be described as a somewhat flattened tube, increasing in width from above downward, the posterior wall of which curves over to form the halfdome-shaped roof. This roof is level with and continuous with the roof of the nasal chambers. The main tunic of the pharynx is a fascia, the shape of which is best described by its attachments. The periosteum lining the inferior surface of the occipital bone is thickened in' the form of a firm plate, termed basilar fibrocartilage. From this fibrocartilage, and as a part of it, the pharyngeal fascia extends downward, being fastened to the slightly protruding body of the atlas, while below the atlas it is separated from the vertebral bodies by loose areolar tissue. Laterally, the curve of the pharyngeal roof extends over to the edge of the inferior surface of the petrous pyramids of the temporal bones, to which the fascia is fastened, and from which it descends. In front the fascia gliding over the short exposed (rear) area of the lower sphenoid surface adheres firmly to the bony rim of the choanæ, and thence passes transversely to the inferior maxilla, where it ends anteriorly. The sides. and posterior wall of the pharynx are completely surrounded by the fascia, which thence continues downward as a lamella of the cervical fascia. The pharynx

proper ends at the level between the fifth and the sixth cervical vertebra. The pharyngeal fascia is lined throughout with mucous membrane, and is surrounded below the atlas by the constrictor muscles of the pharynx. From the foregoing description it is apparent that the pharynx has no real anterior wall. Below its roof are the nasal openings. Between the nasal passages and the cavity of the mouth is the bony palate, the plane of which is prolonged by the soft palate. The latter is a muscular diaphragm lined by nasal mucous membrane on its upper, and by buccal mucous membrane on its under surface. The muscular fibers converge into the palate from the base of the skull, rim of the choanæ, and pharyngeal walls, and end in a tendinous aponeurosis inserted into the rear border of the bony palate. The free posterior border of the soft palate is concave, but with a pendant tongue-shaped prolongation from its center—the uvula. Inspection shows that on each side of the uvula there arises a fold or ridge in the mucous. membrane of the palate, parallel with the posterior free border, running transversely to the insertion of the palate at the roof of the mouth. There the posterior palatal border continues downward in the form of another fold of mucous membrane running down and somewhat backward, the posterior pillar of the fauces,-while the aforesaid palatal ridge descends on the side of the mouth as the anterior pillar down to the root of the tongue. By the divergence of the pillars a niche is formed for the tonsil. During the act of swallowing and gagging the faucial pillars protrude in the form of a well-defined septa under the constricting influence of the muscles external to the mucous membrane. During such movements the palate is stretched tense and maintained in the horizontal plane, so as to separate the nasal from the oral part of the pharynx. When relaxed, however, during rest, the rear part of the palate curves downward.

In the triangular niche between the faucial pillars, normally quite shallow, lies the tonsil. The normal tonsil

is a thin cushion of adenoid tissue in the substance of the mucous membrane. In our climate it is more often seen morbidly enlarged than normal. Across the base of the tongue there stretches a bridge of adenoid tissue from one tonsil to the other-the lingual tonsil. The (incomplete) ring of lymphatic tissue in the pharynx surrounding the buccal opening is completed by a cushion of adenoid tissue in the mucous membrane at the roof, immediately behind the choana-the pharyngeal tonsil.

The cartilaginous portion of the Eustachian tubes lies underneath the lateral walls of the pharynx, outside of the fascia. As these tubes expand in passing forward, downward, and slightly inward, the side of the pharynx is made to bulge inward in the form of a flattened elevation. In front of this tumefaction, at the level and back of the end of the inferior turbinal, is the Eustachian orifice. By reason of the divergence of the anterior and posterior lips of the Eustachian orifice the pharyngeal end of the tube appears as an irregular triangle of a yellowish-white color. The (variable) prominence of the Eustachian tube forms a recess at what might be called the junction of the lateral wall of the pharynx with the superoposterior wall-the fossa of Rosenmuller. This recess becomes shallower downward and ceases just above the level of the palate.

The caliber of the pharynx is, of course, influenced by movements of the head. When the head is inclined backward, the distance between the palate and posterior wall is lengthened, whereas by depression of the head it is shortened. When the head is turned to the side by rotation upon the axis (second vertebra), torsion of the pharynx, which is observable through the mouth, results.

7. The Membranous Lining of the Respiratory Passage. -The entire respiratory passage is lined by a continuous mucous membrane, which extends into all communicating passages and sinuses. In the nose it is thickest over the inferior turbinal, becoming thinner in the higher regions and still more reduced in the pneumatic cells and

accessory sinuses. Close examination shows a somewhat uneven surface of the nasal mucous membrane, with minute ridges and furrows and miniature wart-like elevations. This unevenness of the surface is often grossly exaggerated in inflammatory hypertrophy. In the pharynx the mucous membrane is smoother but thicker; it is especially massive, however, where it is infiltrated with adenoid tissue so as to form the different tonsils. In the nose and accessory cavities the mucous membrane is inseparable from the periosteum. The transition from skin to mucous membrane begins at about the level of the projecting fold in the vestibule. Beyond this threshold, throughout the nose and pharynx, the membrane contains an abundance of branched tubular mucous glands; in the nasal sinuses, however, the glands are few in number. The surface epithelium consists of stratified cylindric cells, of which those on the free surface are ciliated. Interspersed are mucus-forming "beaker cells." In the pharynx, at about the level of the second vertebra, the epithelium changes into stratified pavement epithelium. The epithelial cells in the interior of the mucous glands are cuboid.

In the upper nasal region, which contains the nerves of smell, the structure of the lining membrane, and also of its epithelium, is peculiar. This area extends over the nasal surfaces above the middle turbinal and anterior to the sphenoid sinus, both on the septum and on the surface of the upper turbinal processes. Here the epithelial cells form large cylinders, not ciliated in the ordinary sense, but presenting a few coarse, hair-like "cilia," non-motile, but presumably the specific end-organs of the olfactory nerve.

Underneath the epithelium there is a well-defined structureless basement membrane, with a multitude of tubular perforations, which are probably the inlets (or outlets?) of the lymphatic system. The substance of the mucous membrane consists of a connective-tissue stroma with elastic fibers. Both connective-tissue and elastic