THE TONGUE. 



813 



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. 



Filiform. 



FH nit form. 



Secondary 

 papillse. 



Circumvallate. 



Artery. 



Vein. 



A rtery. 

 Vein. 



FIG. 429. The three kinds of papillae, magnified. 



The papillce maximce (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 -^ 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. 



Immediately behind the apex of the V is the foramen caecum, mentioned above. 

 This, according to His, represents the remains of the invagination which forms the 

 median rudiment of the thyroid body, and for a time opens by a duct, the thyro- 

 glossal duct, on to the dorsum of the tongue. It may extend downward toward 

 the hyoid bone. Kanthack, however, disputes this view. 1 



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 

 extremities, and covered with secondary papillae. Their epithelial investment is 

 very thin. 



The papillce minimce (conicse or filiformes) cover the anterior two-thirds of the 

 dorsum of the tongue. They are very minute, more or less conical or filiform in 

 shape, and arranged in lines corresponding in direction with the two rows of the 

 papillae circumvallatae, excepting at the apex of the organ, where their direction 



1 Journal of Anat. and Physiol., 1891. 



