310 



LECTURE XIV. 



dogs from the same litter and about the same weight, are permitted to fast 

 for quite a length of time. One of the animals is then killed, and the 

 amounts of albumin and fat contained in the carcass are determined. 

 The other animal, which is assumed to possess approximately like quan- 

 tities of the above substances, is then fed for a time on a definite diet, 

 the composition of which in fat, albumin, and carbohydrate is known. 

 The unabsorbed part of this material can be estimated by an analysis of 

 the faeces. After several days, this animal, which has now gained in weight, 

 is killed, and the amount of its fat and albumin determined. In this 

 manner it can be shown that as much as 85 per cent of the ingested starch 

 has been converted into fat. We must not place too much confidence in 

 these values, for the assumption that the one animal, at the termination 

 of the fasting period, contained exactly the same amounts of fat and 

 albumin as the other, is open to question. It is remarkable, nevertheless, 

 that there should be such great differences between the organisms of the 

 two animals, and that corresponding results have been obtained in a 

 number of experiments. . 



Thus, Tscherwinsky * obtained the following values: 



The animal used in the experiment, a young pig, had, therefore, gained 

 7 . 9 kilograms fat, which could not have come from the fat in the food, 

 and certainly not from the albumin. Carbohydrates, therefore, were trans- 

 formed into fat. 



We can, as we have said, also follow the respiratory exchange in an 

 animal fed on a diet rich in carbohydrates. If we know the amounts of 

 carbon, albumin, and carbohydrate present in a food poor in fat, but rich 

 in carbohydrates, we can, on the one hand, by determining the nitrogen in 

 the urine, estimate the amount of albumin retained in the body, and, on 

 the other hand, we can estimate the quantity of carbon remaining in the 

 organism, by determining the amount exhaled as carbon dioxide in addi- 

 tion to that eliminated as urea. In this way it has been found that the 

 amount of carbon retained may be so large that the only possible explana- 

 tion is that the ingested carbohydrates have been converted into fat. 



The production of fat from the sugars has, a priori, much in its favor. 



1 N. Tscherwinsky: Landw. Vers-sta. 29, 317 (1883). 



