116 ORGANISM AND MECHANISM 



quito in line with those that occur in conditions apart from 

 living creatures altogether; but (2) that at present, without 

 going far, we are met by certain difficulties which suggest 

 that we should be cautious before concluding that the phy- 

 sico-chemical re-descriptions of vital events are adequate or 

 on the way towards adequacy. It is certain that some bodily 

 occurrences admit of mechanistic description and that this 

 is very useful, both practically and theoretically. Thus the 

 production of animal heat, which was a riddle to the old 

 physiologists, has in great measure been accounted for just 

 as one might account for the heat in a basin of water after 

 electric discharges have been passed through. The clearing 

 up of this problem may be practically useful to us on a cold 

 day or to our physician if we are fevered. It has also been 

 theoretically useful in the science of physiology, for in- 

 stance because it brought into prominence the more intricate 

 problem of the regulation of the body temperature, which 

 does not seem to admit at present of mechanistic solution. 

 This example seems to us to be typical. Along many lines 

 we advance so far with mechanistic formulation, and then 

 we are suddenly pulled up. Let us, then, methodically test 

 the mechanistic descriptions of occurrences in the realm 

 of organisms, keeping in view both the degree of complete- 

 ness in the descriptions and their relevancy in biological 

 study. It will conduce to clearness if we omit in the mean- 

 time all reference to conscious control. let us consider (1) 

 the everyday functions of the body, (2) animal behaviour, 

 (3) development, and (4), very briefly, evolution. 



