2!J6 



PHYSIOLOGY FOR DENTAL STUDENTS. 



on these hairs that certain dissolved substances set up a stimulus 

 of taste. This stimulus is then conveyed by fine nerve filters 

 which arborize around the taste cells, to the chorda tympani and 

 lingual nerves in the anterior portion of the tongue and the 

 glossopharyngeal in the posterior part. Through these nerves 

 the sensations are carried to the combined afferent nucleus of 

 the fifth and ninth nerves in the medulla oblongata (see Fig. 

 59). 



Fig. 59. Schema to show the course of the taste fibers from tongue to 

 brain (Gushing). The dotted lines represent the course as indicated by rustl- 

 ing's observations. The full black lines indicate another path by which the 

 impulses may reach the brain. (From Howell's Physiology.) 



Substances cannot be tasted unless they are in solution, thus 

 quinine powder is tasteless. One of the functions of saliva is 

 to bring substances into solution in order that they may be 

 tasted. 



There are four fundamental taste sensations: sweet, saline, 

 bitter and sour or acid. The ability to distinguish each of these 

 tastes is not evenly distributed over the tongue, but occurs in 

 definite areas which car) be mapped out by applying solutions, 



