558 



PHYSIOLOGY 



produced by the combination of these amino -acids, as well as the 

 peptones derived from the hydrolysis of proteins, have a bitter taste. 

 Most of the alcohols and sugars have a sweet taste, while the metallic 

 derivatives of these substances are bitter. We do not yet under- 

 stand the law which determines whether any given substance shall 

 have a taste at all, and what its taste should be. 



The nerves of taste are the glossopharyngeal, which supplies the 

 back part of the tongue, and the lingual branch of the fifth nerve 

 and the chorda tympani, which supply the front part. All these fibres 

 are probably connected with a continuous column of grey matter 



G&SSrii.n Ganglion 



Tongue 







FIG. 243. Diagram showing origin and course of the nerve fibres of taste. 



in the brain stem, which represents the splanchnic afferent nucleus 

 of the fifth nerve, the nervus intermedius, and the glossopharyngeal. 

 Some authors have stated that all the taste fibres of the fifth nerve 

 are derived from the glossopharyngeal by the communication through 

 the tympanic plexus and the chorda tympani nerve, while Gowers 

 has recorded a case of complete unilateral loss of taste in which there 

 was a lesion destroying the fifth nerve, the glossopharyngeal being 

 intact. It seems possible that the actual region of the taste-nerve 

 may vary, the fibres running to the splanchnic column of grey matter 

 being contained sometimes in the fifth, sometimes in the glosso- 

 pharyngeal, and sometimes in both. 



Most of our so-called tastes should rather be designated flavours, 

 and are dependent, not on the gustatory nerves, but on the sense of 

 smell. When the olfactory sense is destroyed very little difference is 

 to be perceived between an onion and an apple. The epicure with a 

 fine palate has really educated his sense of smell and would be but 



