III. 



THE NEW PHYSIOLOGY. 1 



Looking back on the history of physiology, we can see 

 that there have been various turning-points in general 

 physiological theory, and consequently in the trend of 

 research. Particular discoveries or series of discoveries, 

 often in allied sciences, have led to these turning-points. 



The last great turning-point in physiology was about 

 the middle of last century. Up till then it was generally 

 held that in a living organism a specific influence, the 

 so-called " vital force," controls the more intimate and 

 important physiological processes. Inspired by the 

 rapid advances of physics and chemistry, the younger 

 physiologists of that time broke away from vitalism, and 

 maintained that all physiological change is subject to 

 the same physical and chemical laws as in the inorganic 

 world, so that in ultimate analysis biology is only a 

 branch of physics and chemistry. 



The subsequent progress of physiology has shown 

 that all, without exception, of the physical and chemical 

 hypotheses then advanced in explanation of intimate 

 physiological processes were far too simple to explain 

 the facts ; but the general conclusion that biology is 



1 A lecture delivered before the Harvey Society, New York, 



October 14, 191(5. 



54 



