484 



TASTE AND SMELL 



Because of the anatomical structure of the taste organ the entrance of the 

 sapid substances in sufficient quantity to arouse gustatory sensations is rendered 

 difficult, especially if the tongue is covered by a thick layer of mucus. 



The taste buds are found chiefly in the circumvallate papilke and in the sides 

 of the foliate papilla?, but occur also in the fungiform papillaa, and are scattered 

 here and there over the various parts of the mucous membrane of the mouth 

 and throat endowed with the sense of taste. 



The tongue possesses also nerves of touch, heat nerves, and cold nerves. 

 What nerves supply gustatory fibers to the tongue can of course only be answered 

 by observations on men in whom the afferent nerves from the tongue have been 

 paralyzed in some way. It appears from such observations summarized by Cas- 



FIG. 191. Course of the facial nerve and its communications with the trigeminal and glosso- 

 pharyngeal nerves. The chief gustatory fibers are indicated in red, after Leube. 



sirer that in by far the greater number of cases the gustatory fibers for the pos- 

 terior part of the tongue traverse the glossopharyngeal, those for the anterior 

 part the basal trigeminal nerve (Fig. 191). In certain cases it appears, how- 

 ever, that the glossopharyngeal represents the gustatory nerve of the whole 

 tongue, while in others it may happen that all the gustatory fibers traverse 

 the trigeminal. 



Only four qualitatively different kinds of sensation are mediated by the 

 sense of taste; namely, sweet, acid, bitter and salt, to which alkaline, and 

 metallic are added by some authors. 



These six qualities however cannot be regarded as pure taste qualities, for 

 all of our gustatory impressions are accompanied by tactile sensations (Kiesow). 



