The Organism and its Chemistry 93 



other animal, for the animal as an animal, the dog as a 

 dog, the ox as an ox, is an avowed concern of his. So it 

 comes about, as said in a former section, that the compara- 

 tive method is fundamental to tlic naturalist. From this it 

 directlv follows that for him differences between organisms 

 are no less basal than are similarities. As a zoologist in the 

 strict sense he is no more concerned with the problem of 

 wherein the bloods of the doo; and the ox are alike than in 

 that of wherein they are unlike. This is so because the dog 

 and the ox being both animals, neither can be to him of any 

 more significance or interest than the other, so that which 

 makes the dog a dog is no more and no less significant than 

 that which makes the ox an ox, and it matters not at all 

 whether the differentiating attributes pertain to the feet 

 or teeth or ears or stomach or blood. See then what this 

 implies as regards the zoologist's attitude toward the chem- 

 ical makeup of the dog and the ox. He wants to know 

 everything about the chemistry of the dog, and also of the 

 ox. It implies that the taxonomizing naturalist must be 

 chemical-minded to some extent and also that the biochemist 

 must be a taxonomic naturalist to some extent. 



That the comparative method, so fundamental and indis- 

 pensable to the naturalist, becomes no less so to the bio- 

 chemist before his work is done, finds no better illustration 

 than in this very problem of the chemistry of the blood. 

 The effects of the bloods of different species of animals upon 

 one another has now become a recognized and important 

 branch of biochemistry. But here is a point the significance 

 of which neither biologists nor chemists appear to have fully 

 grasped : the discoveries in this field could not have been 

 made by any other means than those by which they were 

 made, that is, by actually mingling the bloods of different 

 animals in the living animals. Chemical discoveries of great 

 importance are here dependent absolutely on one of the 

 naturalisfs most cherished methods, the comparative, the 



