182 RESPONSE IN THE LIVING AND NON-LIVING 



animal tissues, must necessarily be irresponsive, or 

 incapable of being excited by stimulus an assumption 

 which has been shown to be gratuitous. 



This ' unexplained conception of irritability became 

 the starting-point,' to quote the words of Verworn, 1 ' of 

 vitalism, which in its most complete form asserted a 

 dualism of living and lifeless Nature. . . . The vitalists 

 soon,' as he goes on to say, ' laid aside, more or less com- 

 pletely, mechanical and chemical explanations of vital 

 phenomena, and introduced, as an explanatory principle, 

 an all-controlling unknown and inscrutable " force hyper- 

 mecanlque." While chemical and physical forces are 

 responsible for all phenomena in lifeless bodies, in 

 living organisms this special force induces and rules all 

 vital actions. 



' Later vitalists, however, attempted no analysis of 

 vital force ; they employed it in a wholly mystical form 

 as a convenient explanation of all sorts of vital phe- 

 nomena. ... In place of a real explanation a simple 

 phrase such as " vital force " was satisfactory, and 

 signified a mystical force belonging to organisms only. 

 Thus it was easy to " explain " the most complex vital 

 phenomena.' 



From this position, with its assumption of the super- 

 physical character of response, it is clear that on the 

 discovery of similar effects amongst inorganic substances, 

 the necessity of theoretically maintaining such dualism 

 in Nature must immediately fall to the ground. 



In the previous chapters I have shown that not the 

 fact of response alone, but all those modifications in 



1 Verworn, General Physiology, p. 18. 



