TASTE AND SMELL. 



[CH. LIT. 



The larger papillae of the-4ongue are thickly set over the 

 anterior two-thirds of its vipper surface, or dorsum (fig. 526), and 

 give to it its characteristic roughness. In carnivorous animals, 

 especially those of the cat tribe, the papillae attain a large size, 



and are developed into sharp re- 

 curved horny spines. Such papillae 

 cannot be regarded as sensitive, but 

 they enable the tongue to play the 

 part of a rasp, as in scraping bones, 

 or of a comb in cleaning fur. The 

 papillae of the tongue present several 

 diversities of form ; three principal 

 varieties may be distinguished, 

 namely, the (i) circumvallate, the 

 (2) fungiform, and the (3) conical 

 and filiform papillae. They are all 

 formed by a projection of the corium 

 of the mucous membrane, covered 

 by stratified epithelium ; they contain 

 special branches of blood-vessels and 

 nerves. 



The corium in each kind is 

 studded by minute conical processes 

 or microscopic papillae. 



(i.) Circumvallate. These pa- 

 pillae (fig. 528), eight or ten in 

 number, are situate in a V-shaped 

 line at the base of the tongue (i, i, 

 fig. 526). They are circular eleva- 

 tions, from zVth to iV^h of an inch 

 wide (i to 2 mm.), each with a 

 slight central depression, and sur- 

 rounded by a circular moat, at the 

 outside of which again is a slightly 

 elevated ring or rampart ; their 

 walls contain taste-buds. Into the 



moat that surrounds the central tower, a few little glands open. 

 They form a thin watery secretion. 



(2.) Fungiform. The fungiform papillae (3, fig. 526) are 

 scattered chiefly over the sides and tip, and sparingly over the 

 middle of the dorsum, of the tongue ; their name is derived from 

 their being shaped like a puff-ball fungus. (See fig. 5296.) 



(3.) Conical and Filiform. These, which are the most abun- 

 dant papillae, are scattered over the whole upper surface of the 



Fig. 527. Section of a mucous gland 

 from the tongue. A, opening of 

 the duct on the free surface : 

 C, basement membrane with nu- 

 clei ; B, flattened epithelial cells 

 lining duct. The duct divides 

 into several branches, which are 

 convoluted and end blindly, being 

 lined throughout by columnar 

 epithelium. D, lumen of one of 

 the tubuli of the gland, x 90. 

 (Klein and Noble Smith.) 



