22 THE FITNESS OF THE ENVIRONMENT 



fidence in his right to make use of the descrip- 

 tion in investigating the relationship between 

 life and the environment. 



The biologist studies living organisms as 

 inhabitants of this world, and by holding 

 fast to physics and chemistry he has created 

 modern physiology, a science which unites 

 many, indeed nearly all, of the departments 

 of physics and chemistry in the task of de- 

 scribing the processes of life. 



That task has proved an arduous one, even 

 in comparison with the other enterprises of 

 science, and it must be confessed that few 

 of the departments of physiology wear an 

 aspect of finality which has long been famil- 

 iar in such sciences as mechanics and crystal- 

 lography, for example. Yet, as time has 

 passed, and the nature of the material basis 

 of life and the conspicuous features of the 

 mechanism which the organism presents for 

 study have become more familiar, assurance 

 has steadily grown of the possibility of decid- 

 ing upon fundamental and essential char- 

 acteristics of the life process. No doubt 

 opinions have fluctuated, and in different 

 periods of the history of science particular 

 phenomena of living organisms have been 

 examined, criticized, and then well-nigh for- 

 gotten. But gradually ideas, ever more and 

 more precise, have arisen and been accepted. 



