1028 SMELL. [BOOK in. 



powerful mechanism. We may perhaps connect with this on 

 the one hand the fact that, even in ourselves, the olfactory fibres 

 have allotted to them what is virtually a whole segment of the 

 brain, namely the olfactory lobe, and on the other hand the fact 

 that olfactory sensations seem to have an unusually direct path 

 to the inner working of the central nervous system. Mental 

 associations cluster more strongly round sensations of smell than 

 round almost any other impressions we receive from without. 

 And powerful reflex effects are very frequent, many people faint- 

 ing in consequence of the contact of a few odorous particles 

 with their olfactory cells. 



The assertion that the olfactory nerve is the nerve of smell 

 has been disputed. Cases have been recorded of persons who 

 appeared to have possessed the sense of smell, and yet in whom 

 the olfactory lobes were found after death to be absent. Direct 

 experiments on animals however shew that loss of the olfactory 

 lobes entails loss of smell. On the other hand, it is stated that 

 section or injury of the fifth nerve causes a loss of smell though 

 the olfactory nerve remains intact ; but in these cases it has not 

 been shewn that the olfactory membrane remains intact, and it 

 is quite possible that, as in the case of the eye, changes may 

 take place in the nasal membrane as the result of the injury to 

 the fifth nerve, sufficient to prevent its performing its usual 

 functions. 



