642 



PHYSIOLOGY 



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 glossopharyngeal, 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. 



G&sseri&n Ganglion 



FIG. 318. Diagram showing origin and course of the nerve fibres of taste. 



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 little satisfied with the simple 

 sensations derived from his four sets of gustatory end organs. 



THE SENSE OF SMELL 



The psychical analysis of olfactory sensations is rendered difficult 

 by the fact that this sense in man plays but a small part in his usual adapta- 

 tions. We have thus to deal with a sense which is in many respects vestigia 1 . 

 We see traces of great complexity in its possibilities of performance, but 

 are baffled in our endeavours to reduce the whole of the phenomena to the 

 simpler factors of which they are composed. Moreover, like all vestigial func- 

 tions, the extent to which the sense is developed varies from one individual to 

 another. Many for instance are unable to appreciate the smell of vanilla, 

 of hydrocyanic acid, or of violets. On the other hand, in animals such as 

 the dog, the olfactory sense seems to play a great part in determining 

 behaviour, and the nervous associations, which are the physiological basis 

 of ideas, must in thc>' animals lx largely connected with olfactory im- 



