THE BEGINNINGS OF LIFE. 47 



definite relation to the amount of work done j and so 

 it may well be that when the nerve-centre is in ac- 

 tion when fains and pleasures are felt, when thoughts 

 are rife this is possible only by reason of a disappear- 

 ance or metamorphosis of a certain amount of potential 

 energy which had previously been locked up in some of 

 the organic constituents of the body. We cannot, how- 

 ever, prove that it is so, because we have not yet been 

 able to show that there is evolved, during brain action, 

 an amount of heat, or other mode of physical energy, 

 less than there would have been had not the Sensations 

 been felt and the Thoughts thought ; and because we 

 have no means of ascertaining what amount of sensa- 

 tion or of thought corresponds to a unit of heat 

 because it is even impossible for us to gauge the strength 

 of a sensation, or the force of a thought we are cut 

 off from all means of comparison. 



Knowing, however, what we now do concerning the 

 evolution of heat in the animal body and concerning 

 the contractility of muscle ; knowing that respiration 

 is, in the main, a process of oxidation j that digestion 

 is an essentially chemical process ; it can no longer be 

 said as of old it was said that the manifestations of 

 Life in organic beings take place independently of 

 physico-chemical laws, and are regulated solely by oc- 

 cult influences. This error has been fast disappearing 

 since Lavoisier sought to demonstrate the real nature 

 of the phenomena taking place in living things, and 

 since he first taught that many of them were essentially 



