66 CROONIAN LECTURES 



ponderable matter and force in the biological 

 sciences have not as yet got beyond the second 

 or Hunterian stage ; and there are many who 

 think that the first stage, which consists in the 

 complete separability between matter and vital 

 force, still represents the whole truth. 



The third stage, or complete union between 

 the ideas of matter and vital force that is, the 

 utter inseparability of one particle of vital 

 force from the matter in which it has been 

 placed, is as yet in its infancy, and cannot be 

 yet subjected to the examination it will have 

 to undergo. 



We are only just entering upon the inquiry 

 how far our ideas of conservation and correla- 

 tion of energy can be extended to the biological 

 sciences. 



We are only just beginning to ask how far a 

 balance can be struck between the income and 

 outgoing of all the energy which vegetables 

 and animals possess in health and in disease. 



The quantity and quality of the energy that 

 comes in, and the quantity and quality of the 

 energy that goes out of the living thing, are 

 questions in every respect as inseparable from 

 the progress of biology, as the quantity and 



