232 THE FITNESS OF THE ENVIRONMENT 



any one of a group of simultaneous reactions 

 that may serve its needs, and make that one 

 predominant. In short, the fitness is recip- 

 rocal ; the unique chemical adaptability of 

 the process and the unique chemical powers of 

 the living organism interlock. 



Such, in brief, are the superlative advan- 

 tages which the properties of the compounds 

 of the three elements contribute to the organic 

 mechanism. They include number of sub- 

 stances, variety of substances, variety of 

 properties, variety of reactions, facility of 

 reactions (instability), and the remarkable 

 relationship between carbon dioxide and water 

 and the carbohydrates. And they insure 

 that extreme variety of chemical relationship 

 which especially fits organic substances, once 

 created, to be, throughout the various forms 

 of life, the source of still other bodies, and the 

 source of energy, by means of far-reaching 

 chemical changes rapidly accomplished. 



G 



HYDROLYSIS 



In the course of digestion the principal 

 foodstuffs, carbohydrates, fats, and proteins, 

 undergo a series of changes which are substan- 

 tially the same for all. Such processes are 

 known as hydrolytic cleavage, or more loosely 



