PHYSICS, BIOLOGY, AND PSYCHOLOGY. 141 



point. These are facts which the mechanical explanation 

 does not account for. 



When we look closely into the changes occurring in a 

 muscle doing muscular work we see that reproduction 

 of the muscular substance is an integral part of these 

 changes. The wonderfully beautiful balance of chemical 

 composition which enables the blood to perform correctly 

 its work in carrying oxygen and carbon dioxide depends 

 no less evidently on constant and minute regulation. 

 The formation and liberation of the digestive ferments is 

 likewise minutely regulated ; and the same is true of the 

 exact form and optical properties of the refractive struc- 

 tures of the eye. Moreover, the whole of these wonder- 

 fully delicately-controlled mechanisms have originally 

 developed from a single cell containing no trace of the 

 future structures. 



It is thus evident that, although we find within the 

 living body many phenomena which, so long as we do 

 not look closely, can be interpreted satisfactorily as 

 physical and chemical mechanism, there are side by side 

 other phenomena for which the possibility of such inter- 

 pretation seems to be absent. The mechanists assume 

 that the bodily mechanisms are so constructed as to 

 maintain, repair, and reproduce themselves. In the long 

 process of natural selection, mechanisms of this sort have, 

 they suggest, been evolved gradually. 



Let us examine this hypothesis. When we state an 

 event in mechanical terms we state it as a necessary 

 result of certain simple properties of separate parts 

 which interact in the event. Thus it is through the 

 interaction of rigid bones of a certain configuration with 

 contractile muscles attached to them at certain points 



