,v>-j Influence of Inanition on Metabolism. 



In experiment No. 76, a redetermination of the fat in the feces changed the 

 result from 3.53 per cent to 7.22 per cent, i. e., it practically doubled the 

 amount of fat in the feces, and reduced correspondingly the percentage of 

 carbohydrates. It was, therefore, decided as the only known method of 

 approximation to the true figures for fat for the feces passed in experiment 

 No. 74 to double the percentage of fat in the two samples, giving, therefore, for 

 No. 3838, 8.82 per cent fat, in place of 4.41, and for No. 3839, 6.56 in place 

 of 3.28, which reduced the carbohydrates in the first instance to 3.52 per cent, 

 and in the second to 12.62 per cent. 



The result of doubling the amounts of fat in these two samples was to 

 bring the heats of combustion as calculated much nearer to the heats of com- 

 bustion found by burning in the bomb calorimeter. The calculated heats of 

 combustion had previously been much lower than those found, namely, 1.256 

 calculated against 1.533 found, and 1.338 calculated against 2.016 found. The 

 calculated results after the fat was doubled were 1.487 calculated against 1.533 

 found and 1.510 calculated against 2.016 found. It seems evident, therefore, 

 that the per cent of fat assumed for No. 3839 is still far too low. 



DIGESTIBILITY OF FOOD IN SHORT EXPERIMENTS. 



Recognizing that feces consist chiefly of metabolic products rather than of 

 undigested food, and in view of the fact that the methods of separating them 

 are imperfect, it is impossible to state absolutely the digestibility of any given 

 food material. In discussing these experiments, the custom is followed of 

 assuming that the feces are composed of undigested food. Since the metabolic 

 products of feces result primarily from the ingestion of food, it is not seriously 

 wrong to make such an assumption. Furthermore, digestion experiments 

 have value only for comparison with previous experiments on digestibility, and 

 consequently it seems best to adhere to the usual method of computation. 



The digestibility of the simple diets given in the short food experiments 

 inside the calorimeter is shown in table 245. 



It was impossible to separate the feces for experiment No. 72, so that no 

 computations regarding the digestibility were made. As is the common 

 experience with diets containing a large amount of milk the digestibility of all 

 the nutrients is high for the three experiments. In experiments Nos. 70 and 

 74, the average digestibility for protein was about 94.5 per cent, fat, 96, and 

 oarbohyd rates, 99 per cent. Slightly more energy was absorbed in experiment 

 No. 74 than in experiment No. 70, the average coefficient of digestibility being 

 92 per cent. In discussing the digestibility of the food in experiment No. 74, 

 it is important to bear in mind that the determinations of fat and carbohydrates 

 in the feces are at best approximate. Indeed, it is very much to be questioned 

 whether in diets so simple as these any appreciable amounts of undigested 

 carbohydrates appear in the feces and in all probability the carbohydrates were 

 completely absorbed. 



