SMELL. 411 



whatever be their shape, the olfactory nerves 

 (n), arising from the anterior lobes (o) of the 

 brain, are distributed ; and the great size of these 

 nerves would lead us to infer considerable acute- 

 ness in the sense which they supply. When 

 the fish is swimming, their situation in front of 

 the snout exposes them to the forcible impulse of 

 the water, which strikes against them. Accord- 

 ing to GeofFroy St. Hilaire, the water enters the 

 cavity by the upper orifice, and escapes by the 

 lower. Scarpa alleges that fishes exercise this 

 sense by compressing the water against the 

 membrane. On the other hand, it is contended 

 by Dumeril, that the perceptions communicated 

 by this organ, being the result of the action of a 

 liquid instead of a gas, should be classed under 

 the head of taste rather than of smell. This 

 seems, however, to be a mere verbal criticism, in 

 making which it appears to have been forgotten 

 that the impressions of odorous effluvia, even 

 in animals breathing atmospheric air, always 

 act upon the nerve through the intermedium of 

 the fluid which lubricates the membrane of the 

 nostril. 



That the nasal cavities of fishes are rudimental 

 forms of those of the mammalia, although they 

 do not, as in the latter class, open into the respi- 

 ratory organs, is shown by the curious transform- 

 ation of the one into the other during the de- 

 velopement of the tadpole, both of the frog and 



