ORGANISM AND ENVIRONMENT 79 



every other aspect. That this is actually so 

 has become more and more clear with the 

 advance of physiology, particularly in recent 

 times. The fundamental mistake of the 

 mechanistic physiologists of the middle of 

 last century was that they completely failed 

 to realise this. Such processes as secre 

 tion, absorption, growth, nervous excitation, 

 muscular contraction, were treated as if each 

 was an isolable physical or chemical process, 

 instead of being what it is, one side of a 

 many-sided metabolic activity, of which the 

 different sides are indissolubly associated. 



The relation of the living organism to its 

 environment is no less peculiar and specific 

 than the relationship of the internal parts and 

 activities of the organism itself. Between 

 organism and environment a constant active 

 exchange is going on. But this exchange, in 

 so far as it has any physiological significance, 

 is always determined in relation to the rest of 

 the living activity of the organism. Whether 

 material is to be taken up or given off, 

 whether and to what extent the organism 

 is to respond to any 'stimulus,' all this is 

 determined in relation to the life of the 



