
RESPIRATION CALORIMETER AND EXPERIMENTS. 213 
of chemical elements and compounds. Men engaged either in 
active work or at rest received certain amounts of food and 
drink daily. The elements and compounds of the food and 
drink together with the oxygen which they used from the 
inhaled air constitute the bodily income. ‘The excreta, solid, 
liquid and gaseous, including the carbon dioxide and water 
exhaled, constitute the outgo. Comparison of the income 
and outgo showed how much of each of the different elements 
and compounds whose quantities were determined were used 
by the men for the support of their bodies and for the work 
which they performed. 
In the description of these experiments it was explained 
that in order to learn satisfactorily just what ingredients of the 
food the body uses to build up its several parts and keep them 
in repair, to make muscular tissue, fat and other materials, and 
to supply the needs of the body for the different kinds of work 
it has to do, experiments were needed in which the income 
and outgo of energy, as well as matter, should be determined. 
To put the statement in another way, if we are going to learn 
just how the body uses the different materials by which it is 
nourished, just what are the values of different kinds of food 
for nourishment, and just what kinds and amounts are appro- 
priate for the needs of people of different classes and with dif- 
ferent occupations, we must be able to compare exactly the 
income and outgo of both matter and energy. The experi- 
ments described in the Report for 1896 above referred to, gave 
_a balance of income and outgo of matter. Those here described 
show the balance of both matter and energy.* ‘The purpose 
of this article is to describe in brief outline so much of the 
apparatus and methods as have to do especially with the in- 
come and outgo of energy, and so much of the later experi- 
ments as bear upon this phase of the subject. 

* A detailed description of the apparatus and the experiments made with it would 
be far to voluminous for the present Report. Such a description is reserved for pub- 
- lication by the U. S. Department of Agriculture through the Office of Experiment 
Stations, in cooperation with which the apparatus has been developed and the experi- 
“ments are being prosecuted. Inasmuch as this Report falls into the hands of many 
who are not specialists in physiological chemistry it 1s thought proper to give herea 
less technical explanation of the apparatus, methods and some of the results of the 
experiments. ; " ’ ; 
The experiments referred to as described briefly in the Report of the Station for 
1896, have been reported in more detail in Bulletin 44 of the Office of Experiment 
Stations of the U. S. Department of Agriculture, entitled *‘ Report of Preliminary 
Investigations on the Metabolism of Nitrogen and Carbon in the Human Organism, 
with a Respiration Cjlorimeter of Special Construction,” by W. O. Atwater, C. D. 
Woods and F. G. Benedict. 
