Vol. 6, 1920 PHYSIOLOGY: ARM SB Y, FRIES AND BRA MAN 
263 
9 Sorensen, S. P. L., Hoyrup, M., Hempel, J. and Palitzsch, S., C. R. trav. Lab. Carls- 
berg, 12, 1917. 
10 Henderson, L. J., Cohn, K. J., Cathcart, P. H., Wachman, J. D. and Fenn, W. O., 
J. Gen. Physiol., 1, 1918-19 (459). 
11 Loeb, J., Ibid., 1, 1918-19 (237). 
THE CARBON DIOXIDE: HEAT RATIO IN CATTLE 
By Henry Prkntiss Armsby, J. August Fries and Winfred 
Waite Braman 
Institute of Animal Nutrition, The Pennsylvania State College 
Communicated by F. G. Benedict, March 24, 1920 
It was recently suggested to us by Dr. F. G. Benedict that if the ratio 
of the carbon dioxide excreted to the heat produced by cattle should prove 
to be sufficiently constant, this fact might be utilized as the basis for 
determinations of the energy metabolism of this species which would be 
approximately correct and which would require only a comparatively 
simple technique. In view of the great value which such a simplified 
method would have, especially for agricultural investigators, and of the 
further fact that a new form of respiration apparatus designed to be used 
in this manner has been constructed by Benedict in cooperation with the 
New Hampshire Agricultural Experiment Station, we have thought it 
worth while to study the results of our calorimetric experiments on cattle 
from this point of view and we present the results of that study here- 
with. ^ 
These experiments were made with the Atwater-Rosa respiration calorim- 
eter which has been in use here since 1901, the heat production as well as 
the elimination of carbon dioxide being measured, and are, so far as we 
are aware, the only direct determinations of the heat production of this 
species. The measured heat production has been compared with the car- 
bon dioxide elimination in 188 24-liour periods.^ The carbon dioxide in- 
cluded, of course, the considerable amount arising from the methane fer- 
mentation in the rumen. The following results were obtained for the heat 
expressed in kilogram calories divided by the carbon dioxide expressed in 
grams. 
Carbon Dioxide : Heat Ratio oe Cattle 
Range 
Mean value 
Standard deviation 
Median 
Theoretical mode 
Error of single variate . . . 
Coefficient of variabiHty. 
2.1500 to 3.1500 
2.4947 ± 0.0085 
0.1713 ± 0.0060 
2.4938 
2.4974 
±0.12 
6.87% 
In 51 of these periods we have also data for the carbon dioxide and heat 
production of the animals in the standing and lying positions respec- 
