THE SENSE ORGANS 



579 



surface of the head as well as on the pharynx. A few teleosts such as 

 amiurus have taste buds on the surface of the trunk, fins, and mouth. 



In amphibia, with the assumption of a land life, taste buds become 

 limited to the tongue and the roof of the mouth. In man, they are found 

 on the tongue, especially on the sides of the vallate papillae, upon the soft 

 palate, and upon the posterior surface of the epiglottis. 



A taste-bud is an ovoid cluster of columnar epithelial cells, each of 

 which extends from the basement membrane to the free surface of the 



EPIGLOTTIS. 





FOLIATE 

 PAPILLAE 



Fig. 478. — The dorsal surface of the tongue. The sulcus terminalis divides the 

 body or apex of the tongue from the root. The two regions have a different embryonic 

 origin. (Redrawn after Sobotca.) 



epithelium. The cells of the outer layer are arranged like the sections of a 

 melon, so that the ends of the cells are brought close together around a 

 small pore, which opens on the surface. Two kinds of cells are differen- 

 tiated, peripheral supporting cells, and sensory taste-cells, which form 

 the core. The sensory cells stain more intensely, and are distinguished 

 by the bristle-like process in which each cell terminates. (Fig. 99) 



To stimulate the taste cells, substances must be dissolved, so that they 

 can penetrate the pore-like opening of the bud. Only four kinds of sub- 

 stances can be tasted by us, sweet, sour, bitter, and salt. Other flavors 

 are smelled, not tasted. 



