SMELL. 121 



Smell. 



Sensations of smell are occasioned when air containing 

 odorous substances in the state of vapour or gas is inspired 

 through the nostrils, but not when the cavity of the nares 

 is filled with their solution. 



Smell is limited to the upper part of the septum, the 

 upper turbinated bone, and the upper part of the middle 

 turbinated bone. This region is characterized by its 

 yellow colour, by its slender columnar epithelial ele- 

 ments, and by the existence among them of the peculiar 

 spindle-shaped elements, which are believed to be the end- 

 organs of the nerve of smell. In inspiration, a large pro- 

 portion of the air inspired passes through the olfactory 

 region ; but, in consequence of the form of the channel 

 through which it passes, the expiratory current is almost 

 entirely diverted, so that odours of intrinsic origin are but 

 little perceived. The varieties of smell are more numerous 

 than those of taste, and appear to have little relation to 

 the chemical constitution of the gases or vapours which 

 occasion them. 



