XXL] 



TONGUE. 



247 



or thirty secondary papillae. Each papilla is composed of fibrous 

 tissue with elastic fibres, and covered by many layers of stratified 

 epithelium, the superficial cells of which are often corneous (fig. 235). 



(2.) Fungiform (0.5-1.5 mm. long), are not nearly so numerous 

 as the foregoing, and are scattered over 

 the doi'sum. Each papilla is club-shaped 

 or lenticular, with a constricted base. 

 The apex is beset with secondary 

 papillae, but the epithelium covering 

 them is thinner than in (i) (fig. 236). 



(3.) Circumvallate (1-1.5 mm - ni S n 

 and 1-3 mm. broad), are confined to 

 the posterior part of the tongue, where 

 they (8-15 in number) are arranged in 

 the form of a V, the apex of the V 

 being directed backwards. Each circu- 

 lar elevation is raised above the level 

 of the tongue and surrounded by a 

 circular trench or fossa. Secondary 

 papillae occur only on their surface. 

 Taste-bulbs occur in the wall of the 

 papilla directed toward the fossa. They 

 are the organs of taste, and are supplied 

 by the glosso-pharyngeal nerve. It may require several sections to 

 obtain views of all three forms of papillae. 



(d.) (H) The stratified squamous epithelium covering the papillae 

 and sides of the tongue. 

 The superficial cells are 

 very thin. 



(e.) Glands, in the 

 back part mucous 

 glands with clear con- 

 tents, and it may be 

 also serous glands in 

 which the acini are 

 more granular (lig. 



237)- 



(/.) Fat-cdls, like 

 padding between the 

 striped muscular fibres 

 here and there. Near 



the lower surface, sections of the lingual artery and nerves, 

 latter cjunglionic, cells may sometimes be seen. 



At the back part of the tongue are little depressions of the 

 mucous membrane called crypts (fig. 237). In the walls of these 



FIG. 235. Filiform Papillfe, x 30. 

 i. Primary papilla; 2. Secon- 

 dary papillae on its summit ; 3. 

 Epithelial process on papilla; 

 4. Single process, with en- 

 tangled loose epithelial cells. 



Secondary 

 papillae. 



Fungiform 

 papilla. 



FIG. 236. Fungiform Papilla, x 30. 



In the 



