' 
242 PRINCIPLES OF ANIMAL NUTRITION. 
the energy content to be from 6.7 to 8.5 Cals. per gram of nitrogen 
in place of 5.4 Cals. as computed on the assumption that only urea 
was present, while for human urine he has obtained values ranging 
from 6.42 Cals. to 8.87 Cals. per gram of nitrogen, and Tang] * 
has reported even higher figures. 
Kellner ¢ has shown that the difference is still greater in the 
urine of an ox receiving only coarse fodder, the actuai energy being 
about six times that computed on the above assumption and nearly 
175 per cent. of that computed after allowing for the hippuric acid 
present. In subsequent investigations { he finds that the energy 
content of the urine of cattle is much more nearly proportional to 
its carbon than to its nitrogen, being approximately 10 Cals. per 
gram of carbon. 
In six cases reported by Atwater & Benedict § in the course of 
their investigations with the respiration-calorimeter, the amount of 
energy found in human urine from a mixed diet as compared with 
that computed from the nitrogen reckoned as urea was: 
Energy. 
Total 
Nitrogen, 
Grms. Actual, | Computed, 
Cals. Cals. 
Experiment No. 5...............00005 72.43 511 392 
ef BES GE dics aaa apm ae aaaee ee 64.29 504 348 
e NES le aes aivtcd cole tg dd ata iat Seca 70.60 569 382 
Ae Ree Oy skated es auoe hy widens amon 77.90 658 421 
ee a ee ee eee ee 71.72 597 388 
ee WS VO because cel eagen ante aanaecs 77.76 589 421 
Here, too, it is evident that a computation on the basis of the 
urea yields results much below the truth, and later experiments by 
the same authors have fully confirmed this result. 
The Feces —Our knowledge of the proximate principles con- 
tained in the feces is so small that no satisfactory computation of 
their energy content is possible, except perhaps in the case of car- 
nivora on a purely meat diet, where the total amount of feces is 
* Arch. f. (Anat. u.) Physiol., 1899, p. 261. 
} Landw. Vers. Stat., 47, 275. 
t Ibid., 58, 437. 
§ U.S. Dept. Agr., Office of Experiment Stations, Bull. 68. 
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