118 



A. I. RINGER 



TABLE VI 



in the form, of fat, we also have a condition of nitrogen hunger and should 

 expect the nitrogen excretion to be on as low a level as in the former case. 

 But this is not so. With fat alone the protein metabolism rises to about 

 double the "minimal" level. A typical experiment is that of Landergren's, 

 which is tabulated here: 



TABLE VII 



On the fourth day the nitrogen reached the "minimal" level which 

 would have continued thus had not the carbohydrates been replaced by 

 fat in the diet. The carbohydrates have the power of sparing body pro- 

 tein to an extent which is not possessed by any other foodstuff. A diet 

 made up so that half the calories are derived from carbohydrates and half 

 from fat will give the same results as a diet consisting entirely of carbohy- 

 drates. 



Landergren assumes that the reason why protein metabolism is higher 

 when carbohydrate is absent from the diet is because a certain amount 

 of protein is destroyed in order to maintain the sugar concentration of the 

 blood, which is always kept at a definite level even during starvation, 

 lie designates that fraction of the protein metabolism as "glucose nitro- 

 gen." This fraction is equivalent approximately to 0.045 gram per kg. 

 of body weight. Rubner and Cathcart have corroborated Landergren's 

 findings, but do not agree with his interpretation. 



