100 LIFE AND DEATH. 



to bring to light the general laws which govern those 

 transformations, and finally to apply them to the 

 detailed study of phenomena. This programme may 

 be divided into four parts. 



In the physical world the specific forms of energy 

 are not numerous. When we have mentioned 

 mechanical, chemical, radiant (thermal and photic) 

 energies, electrical energy, with which is blended 

 magnetic energy, we have exhausted the catalogue of 

 natural agents. 



But is this list for ever closed ? Are vital energies 

 comprised in this list? These are the first questions 

 which we must ask ourselves. 



The iatro-mechanical school, on a priori grounds 

 give an affirmative answer. No doubt there are in the 

 living organism many manifestations which are pure 

 physical manifestations of known energies, mechanical, 

 chemical, thermal, etc. But are all the manifestations 

 of the living being of this order? Are they all, hence- 

 forth, reducible to the categories and varieties of energy 

 which are investigated in physics ? This is the claim 

 of the mechanical school. But the claim is rash. Our 

 fundamental postulate affirms, in principle, that uni- 

 versal energy is manifested in living beings ; but, as a 

 matter of fact, there is no reason for the assertion that 

 it does not assume particular forms, according to the 

 circumstances peculiar to the conditions under which 

 they are produced. 



These special forms of energy manifested in the con- 

 ditions suitable to living beings would swell the list 

 drawn up by the physicists. And it would not be the 

 first instance of an extension of this kind. The 

 history of science records many remarkable cases. 

 Scarcely a century has passed since we first heard of 



