I92 STORRS AGRICULTURAL EXPERIMENT STATION. 
portion of the diet, but obviously there are no such actual 
determinations for the portion of the feces due to cereal. The 
energy in this case is found by subtracting from the energy of 
total feces the computed energy of the part of the feces ascribed 
to food other than cereal. The energy lost in the urine is 
found for the cereal alone in the same manner as for the total 
diet, namely, by multiplying the available protein of the cereal 
by the factor 1.25. 
The energy of the part of the feces estimated to be due to 
food other than cereal was calculated from the amount of protein, 
fat and carbohydrates in it. Previous investigations* have 
shown that the heats of combustion of the nutrients in an 
ordinary mixed diet average per gram as follows: for protein, 
5.65 calories, for fat 9.4 calories, and for carbohydrates 4.15 
calories. In lack of any corresponding factors for the ingre- 
dients of feces, these values were used. But the heat of com- 
bustion of the total feces as calculated by the use of these fac- 
tors varies somewhat from the heat of combustion as actually 
determined; and it seems reasonable to suppose that there 
would be a corresponding variation between the computed heat 
of combustion of the feces from food other than cereal and the 
actual determination if such could be made. In computing the 
energy of this part of the feces, therefore, it was assumed that 
the ratio of the computed heat of combustion of the total feces 
to the heat of combustion as actually determined was the same 
as the ratio of the computed heats of combustion of the feces 
from food other than cereal to the actual values. 
For example: in experiment No. 558 (Table 84, p. 196), the 
computed heat of combustion of the total feces was 680 calories, 
whereas the value as actually determined by the bomb calorim- 
eter was 787 calories. The computed heat of combustion of 
the part of the feces pertaining to food other than cereal was 
350 calories; and the actual heat of combustion was therefore 
assumed to be the fourth term in the proportion 680:787 = 
350:xX, in which case x = 406 calories. , 
This figure being obtained, the next step is to find the energy 
of feces from cereal alone, by subtracting this quantity from the 
determined heat of combustion of the total feces, which gives 
(787 — 406 =) 381 calories. The proportion of energy in the 
* Storrs Expt. Sta. Rpt. 1899, p. 104. 

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