732 



TASTE 



[CH. LIIL 



The middle of the dorsum of the tongue is not endowed to any 

 great degree with the sense of taste; the tip and margins, and 



FIG. 532. Surface and section of the fungiform papilla. A, The surface of a fungiform papilla, partially 

 denuded of its epithelium; p, secondary papillae; e, epithelium. B, section of a fungiform papilla 

 with the blood-vessels injected ; a, artery ; v, vein ; c, capillary loops of similar papillae in the 

 neighbouring structure of the tongue ; d, capillary loops of the secondary papillae ; c, epithelium. 

 (From Kcilliker, after Todd and Bowman.) 



especially the posterior third of the dorsum (i.e., in the region of the 

 taste-buds), possess this faculty. The anterior part of the tongue is 

 supplied by the lingual branch of the fifth nerve and the chorda 

 tympani, and the posterior third by the glosso-pharyngeal nerve. 

 Considerable discussion has arisen whether there is more than one 

 nerve of taste. The view generally held is that the glosso-pharyngeal 

 nerve is the nerve of taste, and the lingual the nerve of tactile sensa- 

 tion. Nevertheless, the lingual and the chorda tympani do contain 

 taste-fibres, which probably take origin from the .cells of the geniculate 

 ganglion ; the central axons of these cells pass by the pars intermedia 

 to the sensory nucleus of the glosso-pharyngeal nerve. Gowers holds 

 that the fifth nerve is the only nerve of taste, and has recorded a case 

 of loss of taste where the fifth nerve alone was the seat of disease ; 

 other cases, however, do not support this view. 



Tastes may be classified into 



1. Sweet. 2. Bitter. 



3. Acid. 4. Saline. 



Whether alkaline and metallic tastes are elementary, is as yet 

 undecided. All the above affect to a varying extent the nerves of 

 tactile sense as well of those of touch proper, sweet having the least, 

 acids the most marked action upon the latter. Sweet tastes are best 

 appreciated by the tip, acid by the side, and bitter tastes by the 

 back of the tongue. 



The substance to be tasted must be dissolved; here there is a 



