272 



THE SPECIAL SENSES. 



nent loss of taste in this region, it follows that the taste fibers do 

 not pass through the Gasserian ganglion. We may assume, there- 

 fore, that they originate directly in the nerve cells of the geniculate 

 ganglion and enter the brain with the fibers of the portio intermedia 

 of the seventh nerve. 



The End-organ of the Taste Fibers. In the circumvallate 

 papillae, in some of the fungiform papillae, and in other portions of 

 the fauces, palate, epiglottis, or even the vocal cords there are 

 found the organs known as taste buds which are believed to act 

 as peripheral organs of taste. These curious structures are repre- 

 sented in Fig. 114. They are oval bodies with an external layer 

 of tegmental or cortical cells, and they contain in the interior a 



number of elongated cells 

 each of which ends in a hair- 

 like process which projects 

 through the central taste 

 pore of the organ. These 

 latter cells may be consid- 

 ered as the true sense cells ; 

 the hair-like process con- 

 stitutes probably the part 

 that is stimulated directly 

 by sapid substances. The 

 impulse thus aroused is 

 communicated through the 

 body of the cell to the 

 endings of the taste fibers 

 which terminate around 

 these cells by terminal 

 arborizations of the same 

 general type as in the case 

 of the hair cells in the 

 cochlea. 



Classification of Taste Sensations. Our taste sensations 

 are very numerous, but it has been shown that there are four 

 primary or fundamental sensations, namely, sweet, bitter, acid, 

 and salty, and that all other tastes are combinations of these 

 primary sensations, or combinations of one or more of them with 

 sensations of odor or with sensations derived from stimulation of 

 the so-called nerves of common sensibility in the tongue. Thus, 

 the taste of pepper may be resolved into a slight odor sensation 

 and a sensation due to stimulation of the fibers of general sensi- 

 bility, that is, it gives no taste sensation proper. The taste of 

 alum may be considered as a combination of a salty taste with 

 common sensibility. Combinations of sweet and acid tastes, sweet 



Fig. 114. Section through one of the taste 

 buds of the papilla foliata of the rabbit (from 

 Quain, after Ranvier), highly magnified: p, Gus- 

 tatory pore: s, gustatory cell; r, sustentacular 

 cell ; m, leucocyte containing granules ; e, super- 

 ficial epithelial cells; n, nerve fibers. 



