84 The Unity of the Orcjanism 



{a) Different Odors and Flavors of Animals and Plants as 



Distinguishable hy Man 



The attciii})t to answer these questions should be prefaced 

 by calHng attention to the fact that experience is very 

 familiar with a group of phenomena that bears directly on 

 the problem even though not much definite chemical knowl- 

 edge of these phenomena has yet been acquired. I refer to 

 the odors and flavors so wide-spread in the organic world. 

 Everybody knows that the odor of the cow is different from 

 that of the sheep, and that that of the pig is different from 

 both. Equally familiar is the fact that the flavor of the 

 meat of these three animals is different. Apples are dif- 

 ferent from pears in both smell and taste, as are peaches 

 from apricots. No one with normal senses of smell and 

 taste would ever mistake potatoes for turnips even though 

 he did not touch or see them. We might go on indefinitely 

 mentioning differences of this sort in both the animal and 

 plant worlds. That these differences have a chemical basis 

 is certain. As is well known, the odors of living animals are 

 to a large extent dependent upon the secretions of various 

 glands of the skin, some of these being sweat-glands and 

 others glands of more specialized character. But the urine 

 and feces contribute much to animal odors, a large number 

 of more or less well known chemical substances being im- 

 plicated ; and the flavors of meat are known to be connected 

 to some extent with the bile. 



These facts of common experience and of fragmentary 

 chemical experience lead naturally to more specific ques- 

 tions in two widely different directions. In the first place 

 we wish to know how far the odor differences, so sharply 

 characteristic of animal and plant groups widely separated 

 from one another in classification, hold as between groups 

 less and less separated ; and second, we inquire whether the 

 chemical differences which reveal themselves by differences 



