PAPILLA OF THE TOXGUE. 703 



forms a tliinner layer than elsewhere, so that these > 

 papillae stand out more prominently than the rest. The 

 epithelium covering the filiform papillae has been shown 

 by Todd and Bowman to have a singular arrangement ; 

 being extremely dense and thick, and, as before men- 

 tioned, projecting from their sides and summits in the 

 form of long, stiff, hair-like processes. Many of these 

 processes bear a close resemblance to hairs, and some 

 actually contain minute air-tubes. Blood-vessels and 

 nerves are supplied freely to the papilla). The nerves in 

 the fungiform and circumvallate papillae form a kind of 

 plexus, spreading out brush-wise (fig. 203), but the exact 

 mode of termination of the nerve -filaments is not certainly 

 known. 



Such, in outline, is the structure of the sensitive surface 

 of the tongue. But the tongue is not the only seat of the 

 sense of taste ; for the results of experiments as well as 

 ordinary experience show that the soft palate and its 

 arches, the uvula, tonsils, and probably the upper part of 

 the pharynx, are endowed with taste. These parts, toge- 

 ther with the base and posterior parts of the tongue, are 

 supplied with branches of the glosso-pharyngeal nerve, and 

 evidence has been already adduced (p. 556 et seq.) that the 

 sense of taste is conferred upon them by this nerve. 



In most, though not in all persons, the anterior part of 

 the tongue, especially the edges and tip, are endowed with 

 the sense of taste. The middle of the dorsum is only 

 feebly endowed with this sense, probably because of the 

 density and thickness of the epithelium covering the fili- 

 form papilla? of this part of the tongue, which will prevent 

 the sapid substances from penetrating to their sensitive 

 parts. The gustatory property of the anterior part of the 

 tongue is due, as already said (p. 547), to the lingual 

 branch of the fifth nerve. 



Besides the sense of taste, the tongue, by means also of 

 its papillae, is endued, especially at its sides and tip, with 



