606 THE SENSES 



in the side walls of the circumvallate papillae. They are also present in the 

 fungiform papillae, in the foliate papillae, and in the mucous membrane. 

 The taste bud is located at the deeper part of the stratified epithelium, is 

 ovoid in shape, and its free end abuts on the surface or opens to the surface 

 by a short canal. It is composed of two kinds of modified epithelial cells 

 the supporting cells, which are long, spindle-shaped cells that form a sheath 

 around the special gustatory cells; and the taste cells, which are neuro-epithe- 

 lial cells that are found in the center of the taste bud. They are very slen- 

 der cells that project on the surface by a delicate process. A bundle of nerve 

 fibrils enters the base of each taste bud and forms a net about the taste cells. 

 The circumvallate, the fungiform, and the filiform papillae, shown in 

 figure 422, are special structures that facilitate the stimulation of the taste 



FIG. 423. FIG. 424. 



FIG. 423. Taste-Bud from Side Wall of Circumvallate Papillae. (Merkel-Henle.) a, Taste- 

 pore; b, nerve fibers, some of which enter the taste bud, intrageminal fibers, while others end freely 

 in the surrounding epithelium, intergeminal fibers. 



FIG. 424. Vertical Section of a Circumvallate Papilla of the Calf, i and 3, Epithelial layers 

 covering it; 2, taste goblets; 4, and 4' , duct of serous gland opening out into the pit in which the 

 papilla is situated; 5 and 6, nerves ramifying within the papilla. (Engelmann.) 



buds by sapid substances. They are all formed by a projection of the mucous 

 membrane, and contain special branches of blood-vessels and nerves. In 

 details of structure, however, they differ considerably one from another. 



Circumvallate Papillce. These papillae, figure 424, eight or ten in number, 

 are situated in tv*o V-shaped lines on the base of the tongue. They are 

 circular elevations from i to 2 mm. in diameter each, with a central depres- 

 sion, and surrounded by a circular fissure, at the outside of which is a 

 slightly elevated ring. Both the central elevation and the ring are formed 

 of close set simple papillae. 



Fungiform Papillce. The fungiform papillae are scattered chiefly over 

 the sides and tip, and sparingly over the middle of the dorsum, of the tongue; 

 the name is deri ed from their being usually narrower at the base than at 

 the summit. They also are supplied with loops of capillary blood-vessels, 

 and nerve fibers. 



