THE FOOD AS A SOURCE OF ENERGY. 303 
_ Crupe Fiser.—In four of his experiments on hay fed alone, 
Kellner * determined the heats of combustion of the crude fiber of 
the food and of the feces with the following results per gram: 
Crude Fiber of | Crude Fiber of 
Hay, Cals. Feces, Cals. 
I....| 4.4350 4.7378 
II....| 4.3907 4.7423 
Ill....| 4.4548 4.9037 
IV....| 4.4230 4.7426 
It appears from these figures that the crude fiber of meadow 
hay has a higher heat value than pure cellulose (4.1854 Cals. accord- 
ing to Stohmann), obviously due to the admixture of compounds 
richer in carbon, while the indigestible crude fiber of the feces has 
a still higher heat value. Merrill + has also reported similar results 
for the crude fiber of oat hay, clover silage, and oat and pea silage, 
as follows: 
Crude Fiber of Fodder. | Crude Fiber of Feces. 
Cals. per Grm. Cals. per Grm. 
Oat hay............- 4.405 4.662 
Clover silage......... 4.610 5.215 
Oat and pea silage.... 4.667 4.820 
It follows that the digested portions of the crude fiber must 
contain less potential energy than the crude fiber of the feed, and 
from the known digestibility of the latter it is easy to calculate 
what the heat of combustion of the digested portion must be. 
Kellner’s results, after deducting 5.711 Cals. per gram for the slight 
amounts of nitrogenous matter still contained in the crude fiber, 
were as shown on the next page. 
The average result shows that not only the chemical com- 
position but likewise the heat of combustion of the digested crude 
fiber varies but little from that of pure cellulose. Merrill’s figures, 
computed in the same manner from the data of the digestion 
experiments reported by Bartlett,t but without the correction for 
* Loc. cit., 47, 299. 
+ Maine Expt. Station, Bull. 67, p. 170. 
{Ibid., pp. 140 and 150, and Report, 1898, p. 87. 
