STARVATION 571 



the starvation amount plus all that we have given as food ; and although 

 by daily giving this amount of protein there may be a slight decline in 

 the excretion, it will never come near to being the same as that of the 

 intake. The only effect of such feeding will be to prolong life for a 

 few days. 



Nitrogenous Equilibrium. To attain equilibrium we must give an 

 amount of protein whose nitrogen content is at least two and one-half 

 times that of the starvation level. For a few days following the estab- 

 lishment of this pure protein diet, the nitrogen excretion will be far in 

 excess of the intake, but it will gradually decline until the two practically 

 correspond. Having once gained an equilibrium, we may raise its 

 level by gradually increasing the protein intake. During this progres- 

 sive raising of the ingested protein, it will be found, at least in the car- 

 nivora (cat and dog), that a certain amount of nitrogen is retained by 

 the body for a day or so immediately following each increase in pro- 

 tein intake. The excretion of nitrogen, in other words, does not immedi- 

 ately follow the dietetic increase. The amount of nitrogen thus retained is 

 too great to be accounted as a retention of disintegration products of 

 protein; it must therefore be due to an actual building up of new pro- 

 tein tissue that is, growth of muscles. 



Nitrogenous equilibrium on a protein diet alone is readily attainable 

 in the cat, and less readily in the dog. But in man and the herbivorous 

 animals, it is impossible to give a sufficiency of protein alone to maintain 

 equilibrium; there will always be an excess of excretion over intake. 

 Indeed it scarcely requires any experiment to prove this, for it is self- 

 evident when we consider that there are less than 1000 C ( in a pound of 

 uncooked lean meat, and that there are few who could eat over three 

 pounds a day, an amount, however, which would scarcely furnish all of 

 the required calories. A person fed exclusively on flesh is therefore 

 being partly starved, even although he may think that he is eating 

 abundantly and be quite comfortable and active. This fact has a prac- 

 tical application in the so-called Banting cure for obesity. 



Protein Sparers. Very different results are obtained when carbohy- 

 drates or fats are freely given with the protein to the starving animal. 

 Nitrogen equilibrium can then be regained on very much less protein, 

 so that we speak of fats and carbohydrates as being (f protein sparers." 

 Carbohydrates are much better protein sparers than fats; indeed they 

 are so efficient in this regard that it is now commonly believed that car- 

 bohydrates are essential for life, and that when the food contains no 

 trace of carbohydrates, a part of the carbon of protein has to be con- 

 verted into carbohydrate. This important truth is supported by evi- 

 dence derived from other fields of investigation (e. g., the behavior of 



