316 PRINCIPLES OF ANIMAL NUTRITION. 
gluten and of beet molasses. The method of computation is pre- 
cisely similar to that already employed for calculating the metabo- 
lizable energy of the total organic matter; that is, the results upon 
the basal ration are subtracted from those upon the ration con- 
- taining the material under experiment. _ 
Taking as an example the results upon wheat gluten with Ox C 
in Periods 1 and 3 we have the following comparison: 
Digested. Gain of 
Energy | Nitrpgen 
Nitrogen of Urine, by 
Protein, | Crude Pe “| Ether ° Cals. Animal, 
Grms. Fiber, Extract Extract. Grms. 
Grms. Gris. Grms. 
Period 3......... 1694 1279 5648 34 2592.8 20.31 
BE OM aniecciccs nia 598 1289 5464 40 1666.4 16.01 
Difference...... 1096 —10 184 —6 926.4 4.30 
The difference of 4.3 grams in the amount of nitrogen gained 
by the animal is equivalent to 32 Cals. which would otherwise have 
appeared in the urine. This added to the 926.4 Cals. actually 
found makes a total of 958.4 Cals. for the increase in the potential 
energy of the urine due to the 1096 grams of protein digested. 
There are also differences in the amount of non-nitrogenous matters 
digested, particularly of the nitrogen-free extract. As Tables I, III 
and IV of the Appendix show, both starch and crude fiber, as repre - 
sented by the extracted straw, tend to diminish the amount of energy 
carried off in the urine. These differences were observed when fron 
2 to 2.5 kilograms of these substances were added to the basal 
ration. If the differences are proportional to the amount fed, the 
energy corresponding to the small difference observed in this ex- 
periment would not exceed 15 or 20 Cals., and may be neglected, 
while the maximum difference in any experiment of the series 
would probably not exceed 70 to 75 Cals. Assuming that all the 
additional protein digested came from the wheat gluten, we have 
for the corresponding energy of the urine 
958.4 1096 =0.874 Cals. per gram protein digested. 
Subtracting this from the total energy of the digested protein as 
found on p. 309, viz., 5.975 Cals., we have 5.101 Cals. as the metabo- 
