CHAPTER XIII 



NUTEITION 



A. THE SOURCES OF POWER AND HEAT FOR THE 

 HUMAN MECHANISM 



1 . Food and nutrition. In general food must meet the 

 following fundamental needs of the body: first, it must 

 supply power for the work of muscles, heart, etc. ; second, 

 it must give, through oxidative or other chemical change, 

 the heat necessary to maintain the body temperature ; third, 

 it must supply all the material needed for the manufacture 

 of everything that enters into the structure of the living 

 cell (growth and repair) and also of the secretions, internal 

 and external, the hormones, and all other special compounds 

 which play any r61e in the working of the human machine. 

 Since the first two of these functions are met by the same 

 food material and in much the same way, we may consider 

 first this aspect of nutrition. 



2. The fuel value of food. In any locomotive engine the 

 same amount of a given fuel will enable the engine to pull 

 a train of the same weight for the same distance over the 

 same track, provided, of course, the engine itself, the bear- 

 ings of the wheels, etc., are in the same condition. When a 

 ton of coal is put into the tender, it is with the expectation 

 that it will move the train a certain distance. Thus there is 

 a definite relation between the fuel burned and the work 

 done. Every engineer knows also that the same weight 

 of different fuels will carry the train different distances; 

 a thousand pounds of wood, of bituminous coal, and of 

 anthracite coal have different fuel values. 



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