128 STORRS AGRICULTURAL EXPERIMENT STATION. 
The conservation of energy in the body.—If the law of the 
conservation of energy obtains in the living organism, the net 
income and the net outgo of energy should be the same. In 
such physiological experimenting, however, it would be hardly 
fair to expect the figures for the two to agree for each day of 
a given experiment, or for each experiment as a whole, even 
if the measurements with the respiration and bomb calorime- 
ters are exact. ‘There may be errors in the estimates of the 
amounts and heats of combustion of the materials actually oxi- 
dized. Variations due to irregularities of the physiological pro- 
cesses of the body are unavoidable and may materially affect the 
results. For instance, the calculations assume that the quanti- 
ties of material in the alimentary canal and of carbohydrates in 
the body as a whole are the same at the end as at the beginning 
of each day or experiment; whereas they may differ considera- 
bly, and the differences would materially affect the results. But 
it might be hoped that if the methods are correct, these errors 
would tend to counterbalance one another in a series of experi- 
ments, and that, in the average of a sufficiently large number, 
the errors would thus be eliminated so that the income and 
outgo would be very nearly the same. 
Exactly this is the case in the data here feported The va- 
riations for individual days, and even those for the individual 
experiments, as shown in the detailed tables of the publications 
mentioned elsewhere* are not inconsiderable; but in the aver- 
age of all the experiments the agreement is very close. Thus 
in twenty-five days of the seven rest experiments with E. O., 
according to the figures for the individual days the net outgo 
varies from 165 calories below to 194 calories above the net 
income. Expressed in percentages of net income, the range 
here is from —6.5 to +9.1 per cent. Both these extremes 
occurred on the first days of the respective experiments. In 
general the results for the first day of an experiment are found 
to be less satisfactory than those for the succeeding days. Con- 
sidering the experiments each as a whole and comparing the 
averages of the several experiments one with another, the 
range of variation is less. Here. the net outgo varies from 103 
calories below to 62 calories above the net outgo per day. Ex- 
pressed in percentages of net income, the range is from —4.1 
* See page 96. 
