THE FOOD AS A SOURCE OF ENERGY. 317 
lizable energy of one gram of digested protein of wheat gluten in 
this experiment. 
For the four experiments upon this substance, computed as in 
the above example, the results were as follows: 
“ Difference in 
pan Energy of Urine.* 
Glut Per Gi f 
Gra. Taek Proteii,, 
Ox B, Periods land 8.............. as 2185 2547.3 1.166 
SE UC) POM OG Bieta dauaine auicvart aad eolereadla wate 1096 958.4 0.874 
Be Ee Ae races nba’ oclule ane vai 1056 1061.1 1.005 
6 ge | MRS oe a ase ace le ave datencgve eiauate arene 1148 1362.1 1.186 
AVCTAS Cis 04 ieee saw e BEG 34 Oe eS 1371 1482.2 1.081 
* Corrected to nitrogen equilibrium. 
Subtracting from the total energy of the digested protein the 
potential energy carried off in the urine we have for the metab- 
olizable energy of one gram of protein 
5.975 Cals. —1.081 Cals. =4.894 Cals. 
If we use Ritthausen’s factor, 5.7, for proteids, the average 
digested protein becomes 1250 grams and the loss of energy in the 
urine 1.190 Cals. per gram of protein. Subtracting this from 6.148 
Cals., the gross energy of one gram of NX5.7 (p. 309), we have for 
the metabolizable energy of the latter 4.958 Cals. per gram. 
The average increase in the energy of the urine for each addi- 
tional gram of nitrogen excreted in these experiments (6.756 Cals.) 
was almost exactly the same as Rubner found in his experiment 
on extracted lean meat (6.695 Cals.). This may be taken as indi- 
cating that the process of proteid metabolism is substantially the 
same in both classes of animals, while the fact that the result is 
notably greater than the energy of urea shows that in the herbivora 
as in the carnivora other waste products than urea result from the 
proteid metabolism. 
In three other experiments beet molasses was added to the 
basal ration, resulting in the digestion of an increased amount of 
nitrogenous matter. Computing the results as in the case of the 
