THE UTILIZATION OF ENERGY. 463 
moved, but the experiments were upon maintenance feeding only 
and afford no data for a computation of utilization. 
A series of respiration experiments on sheep was made by 
Kern & Wattenberg at the Gottingen-Weende Experiment Station 
in 1879, the results of which were reported after Kern’s death by 
Henneberg & Pfeiffer.* Varying quantities of nearly pure proteids 
(conglutin or flesh-meal) were added to a basal ration of hay and 
barley meal, the amount of proteids in the ration being regularly 
increased by about 50 grams in each of four successive periods and 
then similarly diminished through three more periods. 
The experiments suffered from some defects in technique which 
later experience has remedied, the results most strikingly affected 
being those for the amount of methane excreted. For the first 
two periods no results are reported; for the remaining periods they 
are quite variable, and those on different days of the same period 
differ widely. The authors consider that their figures represent 
the minimum amount present, and in their final computations use 
the average of all the five periods as the basis for estimating the 
quantity of carbon excreted in this form. The amounts as actually 
determined showed a considerable diminution in the periods in 
which most proteids were fed, contrary to Kihn’s results, but it is 
worthy of note that the average proportion of carbon dioxide to 
methane was not much different from that found by the latter. 
The determinations of carbon dioxide in the respiratory products 
likewise showed considerable fluctuations from day to day, but as 
the results are mostly the average of three or four trials of twenty- 
four hours each it may be assumed that these variations are more 
or less compensated for. The respiratory products were determined 
for both animals together, although ail the other data were secured 
for each individual. The results given on the following pages, 
therefore, are the totals for both animals. 
It is stated that addition of proteids to the ration resulted in 
the diminution, and final disappearance in the middle period, of the 
hippuric acid of the urine, but the actual amounts present are re- 
ported only for the first and last periods. It is not possible, there- 
fore, to make any satisfactory computation of the energy of the 
urine or of the proper factor for the metabolizable energy of the 
digested proteids of the total ration. By another method of com- 
* Jour. f. Landw., 38, 215. 
