498 PHYSIOLOGY. 



Day of Fast. Proteid in Grams. Fat Used. 



1 104 Not estimated 



10 51 170 



20 33 170 



29 31 103 



Here the stored fats were the chief source of energy. 



In starvation the heart wastes but little it lives upon the pro- 

 teids in the tissues; the central nervous system loses 3 per cent, of 

 its weight; 97 per cent, of the fat is used up, and the muscles lose 30 

 per cent, of their weight. If a starving man is suddenly supplied 

 with proteid food, the man is unable to avail himself of the proteid 

 so abundantly supplied, for only a small part of the proteid ingested 

 is retained or stored up. Hence the fasting man can replace his pro- 

 teid losses in a slow manner, even when he has an abundance of meat. 



Composition of the Body. 



An analysis of a body, as a whole, is represented as follows : 



Water 64 per cent. 



Proteids 16 per cent. 



Fat 14 per cent. 



Salts 5 per cent. 



Carbohydrates 1 per cent. 



The constituents of the body must be constantly replaced by 

 foods. To determine the quantity of the different foods required, is a 

 study of diets. 



Diet. 



The diet of a healthy man has for its aim not only to cover any 

 deficit without catabolism ceasing and of maintaining the system in a 

 state of integrity indispensable to its physiological functions. It also 

 must furnish to the organism a certain food reserve so that the body 

 will not lose its own proper tissue. To ascertain exactly the quantity 

 of nourishment necessary to keep the body-weight the same, it is 

 necessary to have recourse to experiments. 



Proteids contain about 16 per cent, nitrogen. 

 52 " carbon. 



7 hydrogen. 



23 " oxygen. 

 0.5 " sulphur. 



Carbohydrates contain carbon 44 per cent. 



hydrogen 6.2 " 



oxygen 49.4 " 



Fats contain carbon 76.5 per cent. 



hydrogen 11.9 



oxygen 11.5 " 





