STARVATION 605 



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 the nitrogen of which is at least two and one-half 

 times that excreted during the starvation level. For a few days follow- 

 ing the establishment 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 the level at which it stands by gradually increasing the protein in- 

 take. During this progressive raising of the ingested protein, it will be 

 found, at least in the carnivora (cat and dog), that a certain amount of 

 nitrogen is retained by the body for a day or so immediately following 

 each increase in protein intake. The excretion of nitrogen, in other 

 words, does not immediate^ follow the dietetic increase. The amount of 

 nitrogen thus retained is too great to be accounted as a retention of dis- 

 integration products of protein; it must therefore be due to an actual 

 building up of new protein 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 though he may think that he is eating abundantly 

 and is quite comfortable and active. This fact has a practical 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 "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 types of investigation (e. g., the behavior of 

 diabetic patients, in whom the power to use carbohydrates is greatly 

 depressed). The marked protein-sparing action of carbohydrates is il- 

 lustrated in another way namely, by the fact that we can greatly 



