2 THE MECHANISTIC THEORY OF LIFE 



from it. All the matter which is found 

 in the body, or which passes from it, can 

 be accounted for by what is taken up 

 from the environment. Of the particular 

 chemical substances, moreover, which have 

 been found in the body a large and ever 

 increasing number can be formed artificially 

 outside it, and there is no reason for believing 

 that any ultimate difficulty will be experi 

 enced in artificially forming any of the 

 chemical substances which have been dis 

 covered, or are ever likely to be discovered, 

 within the body. 



Another fundamental fact is that the whole 

 of the ejiergy which is liberated in the body, 

 whether as heat, mechanical work, or in other 

 forms, can be traced to sources outside the 

 body. The actual external sources of energy 

 in the living body were first pointed out in 

 general terms by Mayer more than 9ia&y 

 years ago, and the exact investigations of 

 subsequent physiologists have completely 

 verified his general conclusions. 



The two great physical laws of conservation 

 of matter and conservation of energy can 

 thus be extended with apparently rigorous 



