164 PRINCIPLES OF ANIMAL NUTRITION. 
results and also observed a production of fat by these animals when 
fed on food from which all fat had been removed. 
Fat.—That the fat of the food may serve directly as a source of 
body fat has been shown by Hofmann,* who fasted a dog for thirty 
days, thus rendering the body almost fat-free, and then fed for five 
days large amounts of fat bacon containing as little lean meat as 
possible, and from which there were digested daily 370.8 grams of 
fat and 49.4 grams of protein. At the end of the five days the 
body of the animal contained 1352.7 grams of fat. Estimating its 
fat content at the close of the fasting period at 150 grams, there was 
produced daily about 240 grams of body fat. According to the 
highest recorded estimates not over 26 grams of this could possibly 
have been formed from the protein of the food. Hofmann also 
shows from the result’of one of Pettenkofer & Voit’s respiration 
experiments, in which meat and fat were fed, that part of the ob- 
served gain of fat must have had its source in the fat of the 
food. 
The latter investigators also showed in the last of the experi- 
ments cited on p. 144 that a large ration of fat alone may result in a 
considerable storage of fat. Most of the experiments by the same 
investigators in which lean meat and fat were fed show not merely a 
diminution of the loss of body fat but an actual increase in its 
amount. (Compare the averages on page 150.) The fact is most 
strikingly shown, however, in a series in which increasing amounts 
of fat were added to a uniform ration of meat which was itself 
sufficient to maintain both nitrogen and carbon equilibrium. The 
results as given by Pettenkofer & Voit + are contained in the table 
at the top of p. 165, those on the basal ration of meat being the 
same as those given also on p. 109 for the first series. 
It is of course possible to interpret these results as showing that 
the fat of the food was oxidized and protected an equivalent amount 
of the non-nitrogenous residue of the proteids from oxidation and 
that the latter were the real source of the fat gained. No necessity 
for such an interpretation is apparent, however, and the direct 
explanation appears the simpler and more natural. 
The results of experiments upon the deposition of foreign fats 
* Zeit. f. Biol., 8, 153. 
t Ibid., 9, 30. 
