THE FOOD AS A SOURCE OF ENERGY. 327 
lizable energy of starch and similar bodies in this animal as equal 
to their gross energy, viz., 4.185 Cals. per gram in the case of 
starch, 
Extractep Srraw.—The two experiments in which extracted 
straw was added to the basal ration, when computed as in the case 
of the starch experiments, give the following results: 
Difference in Carbohydrates 
Digested. Difference in 
Energy of 
Nitrogen-free ee 
.- i - 4 
“Gras | Extract, 
Ox H, Period 5............... 2046 439 1425.1 
We or aD ase rearaaees Sates 1987 449 1425.2 
i Se Ree 4033 | 888 2850.3 
The loss of energy in the hydrocarbons equals 0.579 Cals. per 
gram of total digestible carbohydrates (of which 82 per cent. was 
crude fiber), and the corresponding metabolizable energy of the 
carbohydrates is 3.668 Cals. per gram. This is a materially lower 
figure than Kellner found for starch and indicates that the loss of 
energy in the gaseous products of fermentation is greater in the 
ease of crude fiber than in that of the more soluble carbohydrates, 
an indication which, as we shall see, is confirmed by the results of 
other experiments. 
CARBOHYDRATES OF Coarse Fopprrs.—Upon the same two 
assumptions, viz., that the carbohydrates are the sole source of the 
gaseous hydrocarbons, and that the latter represent the entire loss 
of energy from the digested carbohydrates, we may compute the 
metabolizable energy of the total digestible carbohydrates of the 
various coarse fodders exactly as in the case of the extracted straw, 
the results being tabulated on the next page. 
If we average the results for each feeding-stuff and compute 
them as in the foregoing cases, our findings are as given on p. 329, 
where the rations are “arranged in the order of their crude fiber 
content. In computing the metabolizable energy, the gross energy 
of the digested carbohydrates has been assumed to be the average 
