192 



PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



lar circumstances takes olfactory notes for the same 

 purpose. 



Judging in the same way, birds are doubtless supe- 

 rior to man, though greatly inferior to mammals. It is 

 commonly supposed that vultures are especially distin- 

 guished for keenness of scent; but experiments of Au- 

 dubon and Bachman show that they are inferior in this 

 respect to dogs. A stuffed deer attracted vultures 

 from the clouds, but dogs paid no attention to it. But 

 a real carcass concealed from view was quickly discov- 

 ered by dogs, while circling vultures did not detect it. 



In all the lower land vertebrates, such as reptiles and 

 amphibians, the olfactory lobes form an important lobe 

 of the brain, and their smell is 

 probably correspondingly devel- 

 oped, but no observations have 

 been made to test it. We there- 

 fore pass on. 



Thus far vertebrates are air- 

 breathing, the odoriferous parti- 

 cles are air-borne, and the smell- 

 ing organs are therefore con- 

 nected with the breathing passages. 

 But fishes breathe water, not air, 

 by gills, not nostrils. Smells with 

 them are therefore water-borne, 

 not air-borne. The organs in 

 fishes are two deep pits near the 

 end of the snout, in the usual 

 position of nostrils, but do not 

 yet open into the throat. The interior of these pits are 

 plicated in a complex manner (Fig. 250, page 369), so 

 as to increase the surface of contact with odorous par- 

 ticles, and large nerves from the olfactory lobes are dis- 

 tributed in them. In sharks, those bloodhounds of the 



Fig. 124. — Brain of a shark : 

 7«, medulla ; c6 t cerebel- 

 lum ; 0, optic lobes ; cr, 

 cerebrum ; of, olfactory 

 lobes ; nc, capsule of the 

 olfactory nerve. { From 

 Gegenbaur. ) 



