540 



THE NERVOUS SYSTEM. 



Epithe- 

 lium. 



Process of 



neuro-epi- 



Nerve- thelial Taste- 

 fibrils, cell. pore. 



.Tegmental 



cell. 

 .Neuro-epithe- 



lial cell. 



Sustentacular 

 cell. 



Terminal 



1 branches of 



nerves. 



FlG. 318. Schematic representation of a taste-goblet (partly after Hermann). 



qualities sweet, acid, bitter, and saline; but to speak of an oily 

 taste is incorrect: such a quality appeals to general sensibility 

 only. The tip of the tongue is most sen- 

 sitive to sweet tastes, the sides to acid, and 

 the back to bitter. 



Conditions of the Sense of Taste. That 

 the sense of taste may be exercised requires 

 the presence of certain conditions, one of 

 which is that the substance must be in a 

 state of solution or be soluble in the saliva. 

 Insoluble substances are tasteless : for this 

 reason calomel is especially suitable as a 

 cathartic for children. Another condition 

 is that the mucous membrane of the mouth 

 must be moist. When the mouth is dry 

 and substances not already in a state of 

 solution are taken in, there is no saliva 

 present to dissolve them ; consequently 

 they are not tasted. This absence of 

 taste is very marked in the parched con- 

 dition of the mouth occurring during 

 fevers. 



To excite the sense of taste, sapid sub- 

 stances must pass by osmosis into the pa- 

 pillae of the mucous membrane and there 

 stimulate the terminal filaments of the nerves which preside over 

 this sense. An important agent in causing this absorption is the 



FIG. 319. Nerve-endings 

 in taste-buds : n, nerve-fibers 

 of taste-buds, 6; i, ending 

 of fibrils within taste-bud ; 

 p, ending in epithelium be- 

 tween taste-buds; s, surface 

 epithelium (G. Eetzius). 



