THE TONGUE. 675 



mucous membrane, which form the glosso-epiglottic ligaments, and with the 

 soft palate and pharynx by means of the anterior and posterior pillars of the 

 fauces. Its apex or tip, thin and narrow, is directed forwards against the inner 

 surface of the lower incisor teeth. The under surface of the tongue is connected 

 with the lower jaw by the Genio-hyo-glossi muscles; from its sides, the mucous 

 membrane is reflected to the inner surface of the gums ; and, in front, a distinct 

 fold of that membrane, ihsfrsenum linguae, is formed beneath its under surface. 



The tip of the tongue, part of its under surface, its sides, and dorsum, jire free. 



The dorsum of the tongue is convex, marked along the middle line by a 

 raphe, which divides it into two symmetrical halves; and this raphe terminates 

 behind, about half an inch from the base of the organ, a little in front of a deep 

 mucous follicle, the foramen csecum. The anterior two-thirds of this surface 

 are rough, and covered with papillae; the posterior third is more smooth, and 

 covered by the projecting orifices of numerous muciparous glands. 



The mucous membrane invests the entire extent of the free surface of the 

 tongue. On the under surface of the organ it is thin and smooth, and may be 

 traced on either side of the frasnum, through the ducts of the submaxillary 

 glands ; and between the sides of the tongue and the lower jaw, through the 

 ducts of the sublingual glands. As it passes over the borders of the organ, it 

 gradually assumes its papillary character. 



The mucous membrane of the tongue consists of structures analogous to 

 those of the skin, namely, a cutis or corium, supporting numerous papillse, and 

 covered, as well as the papillae, with epithelium. 



The cutis is tough, but thinner and less dense than in most parts of the skin, 

 and is composed of similar tissue. It contains the ramifications of the nume- 

 rous vessels and nerves from which the papillae are supplied, and affords inser- 

 tion to all the intrinsic muscular fibres of the organ. 



The papillae of the tongue are thickly distributed over the whole of its upper 

 surface, giving to it its characteristic roughness. They are more prominent 

 than those of the skin, standing out from the surface like the villi of the intes- 

 tine. The principal varieties are the papillae minimse (circumvallatas), papillae 

 mediae (fungiformes), and papillae minimae (conicee or filiformes). 



The papillse maximse (circumvallatae) are of large -size, and vary from eight 

 to ten 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 backwards 

 and inwards, meet in the middle line, like the two lines of the letter Y inverted. 

 Each papilla consists of a central flattened projection of mucous membrane, cir- 

 cular in form, from 2 ' a to T '. 3 of an inch wide, attached to the bottom of a cup- 

 shaped depression of the mucous membrane ; the exposed part being covered 

 with numerous small papillae. 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. The fissure corresponding to the papilla, which is situ- 

 ated at the junction of the two lines of the circumvallate papilla, is so large 

 and deep, that the name foramen csecum has been applied to it. In the smaller 

 papillae, the fissure exists only on one side. 



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

 scattered irregularly and sparingly over -the dorsum of the tongue ; but arc 

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

 other papilla, 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 invest- 

 ment is very thin. 



The papillse minimse (conicee, 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 is transverse. The filiform papillas are of a whitish tint, owing to the 



