O'SnEA ASPECTS OF MENTAL ECONOMY. 73 



CHAPTER III. 



EELATIVE VALUE OF FOODS IN THE PRODUCTION OF NERVOUS 



ENERGY. 



§1. Philosophy of Nutrition. — It is no doubt known to every 

 one that the primary function of food in the system is to sup- 

 ply the force or forces required for the maintenance of the 

 activities of life. The organism may be considered from this 

 point of view as a mechanism designed to accomplish a certain 

 amount of work, physical or mental ; and in effecting this the 

 energy represented in the thing done, including all accessory 

 expenditures and waste, must balance that expended by the doer r 

 thus conforming to the principle of the conservation of energy. 

 The work thus required to be performed by every organism 

 and entailing dissipation of vital energy may be regarded as 

 of two kinds; in the first place the body must be kept up to 

 a temperature quite above that of the environment in which 

 it is ordinarily placed, and a large amount of force must there- 

 fore be transformed into heat. Then there is in every instance, 

 though differing with different people, a characteristic amount 

 of energy employed in muscular and mental activity. In these 

 two directions force is being constantly utilized, and it must 

 be as constantly replenished by the processes of nutrition if 

 life is to be maintained 



The factor of heat seems to be a practically uniform one 

 for all people, since if in any case the body fall far below a 

 certain standard the delicate adjustments essential for the per- 

 petuation of the organism are disturbed and physical annihi- 

 lation ensues. And by virtue of a comprehensive law of be- 

 ing, whereby all possible effort will be made to prevent the 

 dissolution of life, the organism will strive in every way to 

 supply the necessary energy for the preservation of normal 



