344 



LECTURE XV. 



amount introduced, it shows that albumin from the body has been decom- 

 posed. Conversely, if the nitrogen eliminated is less than that ingested, 

 then we are justified in concluding that albumin has been accumulated. 



The following table will give a summary of some of Atwater's experi- 

 ments : 



From these experiments we find, in agreement with those of Voit, that 

 carbohydrates as well as fats act as sparers of albumin, under the given 

 conditions. The fact that in the carbohydrate experiments there was 

 invariably more nitrogen in the faeces than in the experiments with the 

 fats, is explained by the nature of the food. Vegetables predominated 

 in the former case, and meat in the latter. We shall see later, that the 

 protein in vegetables is utilized to a less extent than that of meat. If we 

 subtract the nitrogen in- the faeces from the total nitrogen of the food, we 

 shall obtain the quantity of nitrogen which the organism has evidently 

 utilized. If we insert these values in the above table, we shall find that 

 less nitrogen was available when carbohydrates were eaten, than when 

 fats predominated in the food. Nevertheless, there was less nitrogen 

 present in the urine in the former case than in the latter, although the 

 difference was not great. 



These experiments still leave one question unsolved: How do the 

 fats and carbohydrates act as sparers of albumin, when they are eaten 

 together? In the above experiments, the food at one time contained 

 protein and fat, and at another time protein and carbohydrate. Under 

 ordinary conditions all three kinds of nutrients, fat, carbohydrate, and 

 protein, are available to the organism. Tallquist 1 has, therefore, studied 



1 F. W. Tallquist: Arch. Hyg. 41, 177 (1902). 



