Preface xiii 



questions of this sort are necessary consequences of progress 

 in information about, and interpretation of living nature, 

 is he able to appreciate fully what I mean by chemical and 

 psychological zoology. Formal biochemistry and animal 

 psychology, that is, the chemistry and the psycliology of 

 laboratories*^ devoted to these subjects, are to my zoological 

 eyes really quite incidental and partial and crude, albeit 

 immensely important. Let one once feel the full weight of 

 the inductive evidence favorable to the hypothesis that every 

 organism whatever performs every jot and tittle of its ac- 

 tivities through chemico-physical agencies, and he must at 

 the same time feel the meagerness and crudity, com})ara- 

 tively speaking, of even the fullest and best laboratory 

 knowledge of those agencies by which he himself, let us say, 

 operates as he carries through and expresses in words an 

 argument like that now occupying us. 



The absolute trustworthiness of the main findings of 

 laboratory biochemistry and its incalculably great impor- 

 tance, but at the same time its great imperfection as com- 

 pared with natural biochemistry, are what especially impress 

 me as I bring my best powers to bear on the deepest, most 

 distinctive problems of anthropological zoology; problems, 

 in other words, of the human animal. 



Sucli an attitude toward biochemistry will, I hope, be 

 recognized even by biochemists as calculated to induce at 

 least a receptive frame of mind toward knowledge in tliis 

 domain. It sliould be one imj)ortant qualification for *' read- 

 ing up" in the domain. But certain it is that something 

 more than a receptive mind is essential to enable one disci- 

 plined in one field of science to be a successful gleaner of 

 ripened fruit in another field. It is not true that all the 

 domains of natural knowledge, highly developed as they now 

 are, are enough alike to make training in any one an ade- 

 quate preparation for acquiring second hand knowledge ir 

 every otlier. At least a background of systematic instruc- 



