626 THE WONDER OF LIFE 



for a formulation of the facts of the way in which the 

 great workshop of the body is regulated, of the way in 

 which the different functions are adjusted to every varying 

 need, of the way in which they work into one another's 

 hands, so that a unified effective life results. To take one 

 instance, it is no longer a difficult physico-chemical problem 

 to account for the ' animal heat ' of the living body (or 

 for a large fraction of it, at any rate), but this does not 

 help us much to account for ' warm-bloodedness ' ; that is 

 to say, for the regulation of heat-production and heat-loss, 

 so that the temperature of the body of the bird or the 

 mammal remains approximately constant whatever the 

 outside temperature may be. Much is known in regard 

 to the so-called ' thermotaxic mechanism ', but the more we 

 know the further off it seems from mechanical explanation. 



If no everyday function of the body has found complete 

 re- description in physico-chemical terms, it follows a 

 fortiori that we are not within sight of an explanation of 

 such fundamental vital processes as growth and repro- 

 duction. As we have already seen, organic growth is no 

 process of passive accretion, it is selective and integrative. 

 The new material is incorporated and unified ; what is 

 added on is related essentially, far more than topographic- 

 ally, to what is already present. The growth is a repro- 

 duction of the specific organization and of no other. 



It may seem strange to assert that even if we had a 

 complete record of all the transformations of matter and 

 energy that go on within the body in all its everyday 

 functions, we should not be answering the biological ques- 

 tions as to the activity of the creature as a whole : What 

 is the ' go ' of this animal, how does it keep agoing, how 

 do the various functions work in a variable way into one 



