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HAND-BOOK OF PHYSIOLOGY. 



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 pro- 

 jections, hair-like in appearance, and in some instances in structure also 

 (Fig. 352). 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 

 ther two varieties of papillae, the circumvallate and ihefungiform. 

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



FIG. 352. Two filiform papillae, one with epithelium, the other without. 35-1. p, the substance 

 of the papillae dividing at their upper extremities into secondary papillae; a, artery, and r, vein, 

 dividing into capillary loops; e, epithelial covering, laminated between the papillae, but extended 

 into hair-like processes, /, from the extremities of the secondary papillae. (From Kolliker, after 

 Todd and Bowman.) 



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

 form papillae forms a thinner layer than elsewhere. The epithelium cover- 

 ing the filiform papillae is extremely dense and thick, and, as before men- 

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

 hair-like processes (Fig. 352). Many of these processes bear a close re- 

 semblance to hairs. Blood-vessels and nerves are supplied freely to the 

 papillae. The nerves in the fungiform and circumvallate papillae form a 

 kind of plexus, spreading out brush-wise (Fig. 350), but the exact mode 

 of termination of the nerve-filaments is not certainly known. 



