NITROGEN BALANCE. 353 



the energy balance showing the average net energy available to the 

 body in the several periods of the experiment, it will be seen that there 

 is a very close correlation between nitrogen loss and low net energy. 

 In general, when the net energy is low, the minus figures appear in large 

 proportion and the loss in nitrogen increases. 



With Squad B the reduction in diet was so great, and the total 

 energy available to the body was so small, that the period was not 

 sufficiently long to bring the body-weight to a level and thus permit the 

 drawing of definite quantitative comparisons between the total caloric 

 intake and the average nitrogen loss. It is clear, however, that the 

 large losses found with these subjects, taken into consideration with 

 the small caloric intake, are fully in accord with the general picture 

 shown for Squad A. 



There seems to be, therefore, some very definite relationship be- 

 tween the total energy intake and the nitrogen loss, a relationship 

 most strikingly shown with Squad A. Indeed, it is not impossible 

 to conceive that were one to adjust the diet so as to obtain nitrogen 

 equilibrium one would also have energy equilibrium.^ This, of course, 

 was by no means clearly and definitely proved, but is strongly sug- 

 gested by the figures in the individual tables for the several men. 



Since the total caloric intake on the average bears a very close re- 

 lationship to the body-weight curve, as shown in figures 57 to 68, we 

 may reason that if the diet had been adjusted to secure nitrogen equi- 

 librium without regard to the calories, the body-weight would have like- 

 wise reached equilibrium. In other words, the loss of nitrogen is 

 directly associated with a loss of body-material, not simply nitro- 

 genous material but that which results in an ultimate material lowering 

 of the body-weight. 



That it would be possible for a group of men to lose from 130 to 

 250 grams of nitrogen over a period of this time and not show pro- 

 found disturbance would, a decade ago, hardly have been believed. 

 Experience with a man who fasted 31 days in the Nutrition Laboratory 

 and during this time lost 277 grams of nitrogen has, however, given us 

 a different impression of the significance of the so-called nitrogen 

 "balance' ' or the loss of nitrogen from the body. It is hardly probable 

 that any great amount of organized body-tissue is disintegrated in 

 this loss of nitrogen. We regret that experimental exigencies were 

 such that we could not determine the blood nitrogen and its appor- 

 tionment. This must remain one of the problems to be solved subse- 

 quently. It seems very clear, however, that when the calories are 

 deficient and the body must draw upon its store for caloric material, 

 there is simultaneously a considerable loss of nitrogen. The potential 

 energy of the protein corresponding to the nitrogen thus lost can not 

 account for any appreciable percentage of the energy lost from the 



1 Klemperer, Zeitschr. f. klin Med., 1889, 16, p. 597. 



