308 THE NERVOUS SYSTEM 



the hippocampus, the posterior and inferior parts of the 

 frontal lobe, and the gyri in relation to the anterior part 

 of the corpus callosum. In animals in which the sense 

 of smell is more acute these parts of the brain and the 

 olfactory lobe itself are much better developed. 



The olfactory epithehum is situated out of the direct 

 hue of the respiratory current. Air is diverted towards 

 it in the act of sniffing. 



The failure of some persons to recognise certain smells, 

 and the fact that the nose may be fatigued to one kind 

 of smell though retaining its sensitiveness to others, indicate 

 that the sense of smell is complex, but no clear analysis 

 of smells has yet been made. The sense of smell must 

 be distinguished from other sensations arising in the nose, 

 e.g. pungent sensations due to stimulation of the fifth 

 nerve. 



As regards the central locaHsation of olfactory sensation, 

 the only experimental observations of positive value are 

 those of Ferrier, who by stimulating the hippocampus 

 induced movements of the nostril on the same side. 



THE SENSE OF TASTE 



Lying in the epithehum of the mouth are small bodies 

 known as taste-buds. They are most plentiful around the 

 circum vallate papilte and upon the fungiform papillse. A 

 few are also found on the wall of the pharynx and cheek. 

 The taste-buds contain the sensory nerve-endings of taste. 

 These are spindle-shaped cells with free processes which 

 project through the small orifice of the taste-bud. Among 

 them are the columnar sustentacular cells. The taste-cells 

 on the anterior part of the tongue are connected with the 

 hngual branch of the fifth nerve and the chorda tympani, 

 those on the back of the tongue with the glossopharyngeal. 

 These nerves make widespread connections in the brain 

 stem. The cerebral locahsation of taste is not known. 



