348 



HANDBOOK OF PHYSIOLOGY. 



"her, are situate in two V-shaped lines at the base of the tongue (1, 1, 

 fig. 240). They are circular elevations from jfath to -^th of an inch 

 wide, (1 to 2 mm.), each with a central depression, and surrounded by 

 a circular fissure, at the outside of which again is a slightly elevated 

 ring, both the central elevation and the ring being formed of close-set 

 simple papillae. 



(2.) Fungiform. The fungiform papillae (3, fig. 240) are scattered 

 chiefly over the sides and tip, and sparingly over the middle of the dor- 

 sum, of the tongue; their name is derived from their being usually nar- 

 rower at their base than at their summit. They also consist of groups 

 of simple papillae (A. fig. 243), each of which contains in its interior u 

 loop of capillary blood-vessels (B.), and a nerve-fibre. 



(3.) Conical or Filiform. These, which are the most abundant pa- 

 pillae, are scattered over the whole surface of the tongue, but especially 



Fig. 243. Surface and section of the fungiform papilla*. A, the surface of a fungiform papilla, 

 partially denuded of its epithelium; p. secondary papillae; e, epithelium. B, section of a fungiform 

 papida with the blood-vessels injected ; ct, artery ; r, vein; c. capillary loops of similar papillae in 

 the neighboring structure of the tongue; d, capillary loops of the secondary papillae; e, epithelium. 

 (From Kolliker, after Toddand Bowman.) 



over the middle of the dorsum. They vary in shape somewhat, but for 

 the most part are conical or filiform, and covered by a thick layer of 

 epidermis, which is arranged over them, either in an imbricated manner, 

 or is prolonged from their surface in the form of fine stiff projections, 

 hair-like in appearance, and in some instances in structure also (fig. 

 244). From their peculiar structure, it seems likely that these papillae 

 have a mechanical function, or one allied to that of touch rather than 

 of taste ; the latter sense being probably seated especially in the other 

 two varieties of papillae, the circumvallate and the fungiform. 



The epithelium of the tongue is stratified with the upper layers of 

 the squamous kind. It covers every part of the surface; but over the 

 fungiform papillae forms a thinner layer than elsewhere. The epithelium 

 covering the filiform papillae is extremely dense and thick, and, as before 

 mentioned, projects from their sides and summits in the form of long, 

 stiff, hair-like processes (fig. 244). Many of these processes bear a close 

 resemblance to hairs. Blood-vessels and nerves are supplied freely to 



