880 



THE ORGANS OF SENSE. 



structure with that lining the rest of the oral cavity. The mucous membrane on 

 the anterior part of the dorsum of the tongue is thin and intimately adherent to 

 the muscular tissue, whilst that at the root is much thicker and looser. It consists 



Filiform. 



Fungi form. 



Secondary 

 papillae. 



Circumvallate. 



Artery. ^\ JpVein. 



A rtery. 

 Vein. 



FIG. 516. The three kinds of papillae, magnified. 



of a layer of connective tissue, the corium or mucosa, supporting numerous papillce 

 and covered, as well as the papillae, with epithelium. 



The epithelium is of the scaly variety, like that of the epidermis. It covers the 

 free surface of the tongue, as may be easily demonstrated by maceration or boiling, 

 when it can be easily detached entire : it is much thinner than on the skin : the 

 intervals between the large papillae are not filled up by it, but each papilla has 

 a separate investment from root to summit. The deepest cells may sometimes 

 be detached as a separate layer, corresponding to the rete mucosum, but they 

 never contain coloring matter. 



The corium consists of a dense feltwork of fibrous connective tissue, with 

 numerous elastic fibres, firmly connected with the fibrous tissue forming the septa 

 between the muscular bundles of the tongue. It contains the ramifications of the 

 numerous vessels and nerves from which the papillae are supplied, large plexuses 

 of lymphatic vessels, and the glands of the tongue. 



The Papillce of the Tongue. These are papillary projections of the corium. 

 They are thickly distributed over the anterior two-thirds of its upper surface, giving 

 to it its characteristic roughness. The varieties of papillae met with are the 

 papillae maximae (circumvallatce), papillae mediae (fungiformes), papillae minimae 

 (conicce or filiformes), and papillae simplices. 



The papillce maxima (circumvallatae) are of large size, and vary from eight to 

 twelve in number. They are situated at the back part of the dorsum of the tongue, 

 near its base, forming a row on each side, which, running backward and inward, 

 meet in the middle line, like the two lines of the letter V inverted. Each papilla 

 consists of a projection of mucous membrane from ^V to y 1 ^ of an inch wide, 

 attached to the bottom of a cup-shaped depression of the mucous membrane ; the 

 papilla is in shape like a truncated cone, the smaller end being directed down- 

 ward and attached to the tongue, the broader part or base projecting on the sur- 

 face and being studded with numerous small secondary papillae, which, however, 

 are covered by a smooth layer of the epithelium. The cup-shaped depression 

 forms a kind of fossa round the papilla, having a circular margin of about the 

 same elevation covered with smaller papillae. At the point of junction of the two 

 rows of papillae is the deep depression, the foramen ccecum, mentioned above. 



The papillce mediae (fungiformes), more numerous than the preceding, are 

 scattered irregularly and sparingly over the dorsum of the tongue, but are found 

 chiefly at its sides and apex. They are easily recognized among the other 

 papillae, by their large size, rounded eminences, and deep-red color. They are 

 narrow at their attachment to the tongue, but broad and rounded at their free 



