CHAPTER XIX 



TASTE AND SMELL 



BY means of the sense of taste we learn something of the solid and fluid 

 substances taken into the mouth, and by means of the sense of smell some- 

 thing of the nature of the atmosphere entering the nasal cavities. The two 

 senses very often work together, and many impressions which we ordinarily 

 describe as sensations of taste, have, as a matter of 

 fact, nothing whatever to do with the sense of taste, 

 being mediated solely by the organs of smell. 



1. SENSATIONS OF TASTE 



Ordinarily only the upper suriace of the tongue 

 is described as the peripheral organ of taste. But 

 this appears to be incorrect, for according to dif- 

 ferent authors the under surface of the tip of the 

 tongue, the soft and hard palate, the anterior pillars 

 of the fauces, the tonsils, uvula, posterior wall of 

 the pharynx, posterior side of the epiglottis and of 

 the larynx, as well as the mucous membrane of the 

 cheeks, mediate sensations of taste. However, this 

 is true only of children ; in adults the mucous mem- 

 brane of the cheeks, the uvula, tonsils and middle 

 of the tongue no longer react to sapid substances; 

 in exceptional cases the anterior pillars of the 

 fauces and the under surface of the tip of the 

 tongue, both sides of the frenum, continue to be 

 percipient. According to Hanig the central zone 



of the tongue which is not percipient is surrounded on all sides by a " taste 

 girdle " within which the sensitiveness decreases more and more from the edge 

 toward the middle line (cf. Fig. 190, where the sensitivity of the different 

 portions is schematically represented by the number of black spots). 



The end organs of the gustatory nerves are the taste buds or taste goblets 

 discovered by Loven and Schwalbe. They are ovoid bodies, 0.08 mm. long and 

 0.04 mm. thick, which lie imbedded in the epithelium of the mucous membrane. 

 They consist in part of outer, sustentacular or tegumental cells and in part of 

 inner taste cells which represent the true neuroepithelium connected in one way 

 or another with the gustatory nerve fibers. In order to stimulate these taste cells 

 the sapid substance must come into actual contact with them, and this is made 

 possible by the presence of a small taste pore at the top of the taste bud, into 

 which the attenuated ends of the taste cells project. 



483 



FIG. 190. The taste zone on 

 the upper surface of the 

 tongue, after Hanig. 



