28 THE NEW PHYSIOLOGY. 



be. Orthodox text-books still, it is true, speak of the 

 " mechanism " of such processes as secretion ; and the 

 unwary are thus led to believe that these processes are 

 more or less understood as physical and chemical pro- 

 cesses. But the blunt truth, enforced again and again 

 by actual investigation, is that if there be any physical 

 or chemical explanation of them, it remains for the 

 present unknown, and with advancing knowledge seems 

 to recede further and further away. This fact is so 

 evident when one looks back over the progress of the 

 last half-century that I need hardly illustrate it. It 

 does not follow, however, that because the supposed 

 physical and chemical processes are too complex for 

 our present powers of analysis, they do not exist. The 

 upholders of the mechanistic theory of life maintain 

 that all the facts hitherto ascertained with regard to 

 the activities of living organisms are simply physical 

 and chemical facts : the movements of living organisms 

 are simply physical movements ; and the chemical 

 products of physiological activity are simply ordinary 

 chemical products. For instance, the oxygen liberated 

 in gas-secretion is simply ordinary oxygen, discovered 

 and measured by ordinary chemical and physical 

 methods. When we set ourselves to the task of physio- 

 logical investigation all we can really do is to investigate 

 the physical causes of the movements and the chemical 

 sources of the products. No other course has any 

 meaning. As a matter of fact, we never actually run 

 up against some mysterious entity, such as the supposed 

 ' vital force." We can always push physical and 

 chemical analysis further ; and there is nothing for it 

 but to pursue this process from the known and firm 



