RELATION OF PHYSIOLOGY TO PHYSICS. 5 



enthusiasmjfor the first kind of knowledge closed their 

 eyes to the second. That time is past, and we must 

 once more face the old problem of life. 



Let us first look at the answer given to this problem 

 by many of the older physiologists. Roughly speaking, 

 they carried physical and chemical explanation of 

 physiological processes as far as they could, and for 

 the rest assumed that at some point or other the physical 

 and chemical factors are interfered with and ordered 

 in a teleological direction by something peculiar to living 

 organisms the " vital principle " or " vital force." 

 This theory, if one can call it a theory, had the nega- 

 tive merit that it did not lead physiologists to ignore 

 facts which they could not explain. In practice the 

 " vital force " became simply a convenient resting-place 

 for these facts. It was assumed that the vital force 

 can do anything and everything, and that it acts " from 

 the blue" on physical and chemical processes. But its 

 action was admittedly dependent on physical and chemical 

 conditions, such as warmth, the presence of oxygen, etc. 

 In fact no consistent definition was given to the con- 

 ception of " vital force." It consequently never could 

 become a working hypothesis of any value. Chiefly on 

 this account, I think, it practically disappeared from 

 physiology last century. Yet the class of fact which led 

 to the theory of " vital force " is now more prominent 

 then ever ; and what du Bois-Reymond called the 

 " spectre " of vitalism meets us at every turn, thinly 

 disguised under such names as " cell autonomy," " vital 

 processes," etc. It is useless to shut our eyes and deny 

 the existence of this " spectre." We must fairly face 

 and examine it. 



