244 THE FITNESS OF THE ENVIRONMENT 



aspect of the chemical reactions into which 

 carbon, hydrogen, and oxygen enter, must be 

 now noticed. 



It has been shown above that the one pos- 

 sible chemical process by means of which any- 

 thing can be made out of the primary con- 

 stituents of the environment is reduction, — 

 the more or less complete tearing off of oxygen 

 from carbon and hydrogen atoms in the mole- 

 cules of carbon dioxide and water. As a 

 function of the extent of the reduction the 

 energy change involved in the process will 

 vary. In all cases, however, the process is 

 accompanied by large absorption of heat, as 

 the following table of the energy absorbed 

 per gram of the resulting substance, when 

 reduction begins with water and carbonic 

 acid, may indicate: — 



Such new compounds hold their energy 

 only so long as they persist unchanged, and 



