THE GENESIS OF FUNCTIONAL INERTIA 119 



than the maximal whether in retina or in muscle. 

 Heart-muscle, however, resembles the chemically 

 explosive living matter in respect of its " all or 

 nothing " behaviour : a weak stimulus as effectually 

 as a strong will bring out the maximal force of systole. 

 The inertial manifestations of cardiac muscle, as we 

 have seen, are very pronounced, and this non-corre- 

 spondence between strength of stimulus and energy 

 of response is but one more expression of them. 



If affectability then is ultimately (causally) based 

 on some molecular grouping peculiar to living matter, 

 so is functional inertia neither more nor less so : 

 functional inertia is no more physical than or is as 

 physical as affectability. 



In this realm of properties behind the phenomena 

 of living matter in which I wish to consider all the 

 diverse vital phenomena as dependent on two funda- 

 mental properties of protoplasm, the concepts 

 " vital " and "bio-chemical," come to be synonymous. 

 When to-day we assert that secretion, absorption, 

 and movement are " vital " phenomena, the outcome 

 of affectability, we do not mean by vital anything 

 more, physico-chemically, than complexity of molec- 

 ular groupings in protoplasm ; and similarly, when I 

 attribute latent period, refractory period, and other 

 insusceptibilities (all equally " vital " phenomena) 

 to the property of inertia in protoplasm, I mean that 

 they also are due to some other and complementary 

 complexities of molecular grouping in the living 

 stuff. 



It is, therefore, highly probable that the property 



