TASTE. 589 



the sensations they arouse, or arrange them in series; and 

 mells are but minor sensory factors in our mental life, al- 

 though very powerful associations of memory are often aroused 

 by odors. AVe commonly refer them to external objects, since 

 we find that the sensation is intensified by ' ' sniffing ' ' air into 

 the nose, and ceases when the nostrils are closed. Their 

 peripheral localization is, however, imperfect, for we confound 

 many smells with tastes (see below) ; nor can we well judge of 

 the direction of an odorous body through the olfactory sen- 

 sations which it arouses. 



Taste. The organ of taste is the mucous membrane on 

 the dorsum of the tongue and, in some persons, of the soft 

 palate and fauces. The nerves concerned are the glosso- 

 pharyngeals, distributed over the hind part of the tongue, 

 and the lingual branches of the inferior maxillary division of 

 the trigeminals on its anterior two thirds. 



On the tongue most of the sensory nerves run to papillae ; 

 the circumvallate have the richest supply, and on these are 

 peculiar end organs (Fig. 174) known as taste buds, they 



FIG. 174. Taste-buds. 



are oval and imbedded in the epidermis covering the side 

 of the papilla. Each consists, externally, of a number of flat, 

 fusiform, nucleated cells and, internally, of six or eight so- 

 called taste-cells. The latter are much like the olfactory cells 

 of the nose, and are probably connected with nerve-fibres at 

 their deeper ends. The capsule formed by the enveloping 

 cells has a small opening on the surface ; each taste-cell termi- 

 nates in a very fine thread which there protrudes. Taste- 

 buds are also found on some of the fungiform papillae, and 

 it is possible that simpler structures, not yet recognized, and 

 consisting of single taste-cells are widely spread over the 



