18S7.J Sayles on the Sense of Smell in Cathartes aura. C 7 



Criticisms. — I have made these quotations in full for the pur- 

 pose of offering a few criticisms, and adding my own observations. 



First point. Mr. Owen, as a comparative anatomist, declares 

 that the olfactories are largely developed. Mr. Owen's testimony 

 on this point I take as entirely satisfactory. Now I boldly chal- 

 lence the world to produce an instance ofa large, well-developed 

 nerve of sense, in any species, which was not so developed by 

 use, and which is not used. This, I think, is pretty good Dar- 

 winism. 



For what, however, does the Turkey Buzzard need a large and 

 well-developed organ of smell? Animals with any large sense- 

 organ need that organ for one of two purposes — either to guard 

 against danger, or to aid in finding food. Hunters, in their 

 search for deer, know well that they must calculate on keeping 

 their quarry at the windward. The deer's sense of smell is keen, 

 and he flies from the tainted breeze at his highest speed. 



The Buzzard does not need the sense of smell for protection 

 against danger. To aid in its search for food is, therefore, 

 its only use in this bird. I might rest my argument right here, 

 and leave it for others to overthrow my position. 



I premise here that I do not call in question the Buzzard's keen- 

 ness of vision. That is granted ; but any experiment that goes 

 only to prove the Buzzard's keenness of vision, by no means 

 proves its sense of smell dull. 



Now, what are the conditions on which the sense of smell is 

 available? First, there must be something to taint the medium, 

 whether water or air. Anglers sometimes put some strong odor 

 on their bait. The water dissolves this, and the fish, under cer- 

 tain conditions, smell it, and rush for it. Something which the 

 air can dissolve is exposed in the air, which the air takes up and 

 diffuses, and animals with a keen sense of smell for this thing 

 speedily find their way to it. Kill any animal by bleeding, dur- 

 ing the warm weather, and that animal will scarcely breathe its 

 last before swarms of the green meat-fly will be humming around 

 it. 



But this is not all. The fish can never smell the tainted 

 water up stream. It must be in the water below the tainted bait. 

 Moreover, the tainted current takes a peculiar form, gradually 

 spreading laterally and up and down, giving to the tainted tract 

 approximately the shape of a cone. 



