

CONSERVATION OF ENERGY IN LIVING ORGANISM. isfel 
The net income of energy of the body is computed from the 
energy of food, drink, solid and liquid excretory products, and 
body material stored or lost, an allowance being made for slight 
changes in temperature of the apparatus and the body during 
the experiment. The net outgo is measured by the apparatus. 
By comparing these the balance of income and outgo of energy 
is found. 
The data for the metabolism of matter and of energy, ob- 
tained as explained above, taken in connection with what is 
known of the physiological processes that go on in the body, 
give more accurate information than can be otherwise obtained 
| regarding the ways in which the food is used in the body, the 
quantities of different food ingredients that are needed to sup- 
ply the demands of the body, the different conditions of rest 
and work, and the comparative nutritive value of different food 
materials. 
THE ACCURACY OF THE APPARATUS AND METHODS. 
Two methods of testing the accuracy of the apparatus are 
employed. By one method known amounts of heat are gener- 
ated electrically within the chamber, and the heat is measured 
by the apparatus. In this way its accuracy as a calorimeter 
only is tested. By the second method known amounts of ethyl 
alcohol of known purity and composition are burned completely 
within the chamber, and the amounts of water, carbon dioxid, 
and heat resulting from the combustion of the alcohol are deter- 
mined by the apparatus. In this way its accuracy both as a 
respiration apparatus and as a calorimeter is tested. In the 
average of five electrical tests the amount of heat measured by 
’ the calorimeter was 100.01 per cent. of the amount generated 
by the electric current. ‘The averages of the results obtained © 
in seventeen alcohol tests are summarized in the following table: 
The results thus indicate that the respiration calorimeter is 
an instrument of precision and that the determinations of car- 
bon dioxid, water, and heat produced within the chamber of 
the apparatus are sufficiently accurate for experiments with 
_ the living subject. 
