CHAPTER III. 



NUTRITION. THE VITAL FORCE. 



THUS we have clearly before us the idea of the 

 organic state as one of tension, dependent upon an 

 opposition to chemical affinities. And we see, too, 

 how this tension is produced, at least in some cases : 

 namely, by the previous operation of those very 

 affinities themselves. But some interesting ques- 

 tions suggest themselves here, to which it is in 

 our power to give at least probable answers. We 

 may ask whether this dependence of the living state 

 on chemical action is universal; or whether other 

 forces, such as light and heat, may not also 

 directly produce it? There appears reason to be- 

 lieve that the latter is not the case; but that a 

 process of chemical change is always connected with 

 the vitalizing of matter, and that any other forces 



