CHAP. XV.] FUNCTIONS OF THE PAPILLAE OF THE TONGUE. 441 



and elasticity ; the latter quality depending on the abundant yellow 

 fibrous tissue they contain, and which, with a wavy, almost spiral 

 character, has a general longitudinal direction (fig. 101, c, c, c}. 

 They are commonly found to .contain tubular nerve-fibres, which we 

 have on several occasions, but not always, seen to terminate in loops 

 (fig. 101, A, B, c). We have usually found it easiest to distinguish 

 the tubular fibres in the papillae at the front of the tongue. 

 The reader will at once recognize the broad and obvious distinc- 

 tion between the papillae last described and all the other varieties, 

 and will probably surmise, on structural grounds, that they can 

 scarcely share in the reception of impressions which depend on the 

 contact of the sapid material with the papillary tissue. The com- 

 parative thickness of their protective covering, the stiffness and brush- 

 like arrangement of their filamentary productions, their greater 

 development in that portion of the dorsum of the tongue which is 

 chiefly employed in the movements of mastication, all evince the 

 subservience of these papillae to the latter function rather than to that 

 of taste ; and it is evident that their isolation and partial mobility 

 on one another must render the delicate touch with which they are 

 endowed more available in directing the muscular actions of the 

 organ. The almost manual dexterity of the organ in dealing with 

 minute particles of food is probably provided for, as far as sensibility 

 conduces to it, in the structure and arrangement of these papillae. 



The simple papillae on the base of the tongue, and those clothing 

 the circumvallate and fungiform papillae, do not appear to differ from 

 one another in any important structural condition, notwithstanding 

 their variety of outward form and arrangement in the compound 

 organs : their epithelium, though of the scaly kind, is very thin, and 

 would easily permit the transudation of sapid substances dissolved 

 in the mucus of the mouth. The softer and perhaps cellulated in- 

 terior of these papillae may have a further influence on the act of 

 sensation. With regard to the use of the singular configuration of 

 the circumvallate and fungiform papillae, it maybe conjectured that 

 the fissures and recesses about their base are designed to arrest on 

 their passage small portions of the fluids in which the sapid mate- 

 rials are dissolved, and thus to detain them in contact with the 

 most sensitive parts of the gustatory membrane. 



We may here allude to a certain gradation that is apparent from 

 the papillae of touch, through those of taste, to the absorbing villi of 

 the small intestines. Touch shades into taste, and at a lower point 

 sensibility is lost. In the tactile papillae, the excitant of the nerves 

 merely comes into contact with the exterior of a thick epidermic cover- 



