PROTEINS AS FAT- AND AS GLYCOGEN-FORMERS 459 



TABLE SHOWING THE OUTPUT OF NITROGEN IN A NORMAL, HEALTHY INDIVID- 

 UAL ON A FOOD RICH IN NITROGEN, JULY 13, AND POOR IN NITROGEN 

 JULY 20TH (FOLIN). 



July i3th. July 2oth. 



Volume of urine . . .1,170 c.c. . 385 c.c. 



Total nitrogen 1 6 . 08 grams 3 . 60 grams 



Urea nitrogen 14. 70 grams =87 . 5 per cent. 22.0 grams =61 . 7 per cent. 



Ammonia nitrogen . 0.49 grams = 3.0 per cent. 0.42 grams = n .3 per cent. 



Uric-acid nitrogen. o.i8grams= i . i per cent. 0.09 grams = 2 . 5 per cent. 



Creatinin nitrogen . 0.58 grams = 3.6 per cent, o . 60 grams = 17.2 per cent. 



Undetermined nitro- 0.85 grams = 4.9 per cent. 0.27 grams = 7.3 per cent, 

 gen. 



Folin states this theory as follows: "It is clear that the metabolic proc- 

 esses resulting in the end products which tend to be constant in quantity 

 appear to be indispensable for the continuation of life; or, to be more defi- 

 nite, those metabolic processes probably constitute an essential part of the 

 activity which distinguishes living cells from dead ones. I would therefore 

 call the protein metabolism which tends to be constant, tissue metabolism, 

 or endogenous metabolism; the other, the variable protein metabolism, I 

 would call the exogenous or intermediate metabolism. 



"The endogenous metabolism sets a limit to the lowest level of nitrogen 

 equilibrium attainable. Just where that level is fixed will depend on how 

 much, if any, urea is derived from the same katabolic processes that produce 

 the creatinin. If this can be determined, we shall have a formula expressing 

 more or less definitely the point of lowest attainable protein katabolism, 

 because at such a point the percentage composition of the urine should be 

 practically constant. The total nitrogen eliminated when this constant com- 

 position of the urine has been reached will indicate the lowest attainable 

 level of nitrogen equilibrium. " 



The condition of nitrogenous equilibrium, therefore, is one which may 

 be maintained even if the amount of protein taken as diet far exceeds the 

 necessities of the economy, the urea being excreted in excessive amount. 

 The wasteful use of protein food which is so prevalent may not be attended 

 with harmful consequences, so long as the excreting organs are able to 

 eliminate nitrogen from the body but it overworks those organs. 



It is only in cases of growth, by putting on of flesh, as in growing children, 

 that nitrogen is retained in the body in health, except to a very small amount. 

 According to calculations which have been made, it appears that the body 

 puts on 30 grams of flesh for every gram of nitrogen so retained. 



Proteins as Fat- and as Glycogen-Formers. Protein food is un- 

 doubtedly a source of energy in the body; and one can say that such protein 

 as is, according to Voit's view, metabolized without becoming part of the 

 tissue may be considered a source of energy. If this be true, one might ex- 



