
CONSERVATION OF ENERGY IN LIVING ORGANISM. 113 
The metabolism experiments included in this discussion com- 
prise two classes. (1) Those in which the subjects were at 
rest, z. €., had no more exercise than was involved in dressing 
and undressing, and caring for the furniture, food and excreta; 
and (2) those in which they were engaged in more or less severe 
muscular work on a bicycle-dynamo apparatus devised for 
measuring the amount of work performed. 
Five different men have served as subjects in these experi- 
ments, all of them young and in excellent health. E. O. was 
a Swede by birth, who has received his training in laboratory 
work in connection with the respiration calorimeter and related 
investigations and is now employed in this laboratory as analyst 
‘and assistant. The rest were university-bred men and natives 
of the United States, except J. F. S. who was a Canadian. 
©O. F. T. and J. F.S. were chemists and A. W. 5S. was a physi- 
cist, all three being assistants in this laboratory; J. C. W. was 
a student in Wesleyan University at the time of the expert- 
ments with him. 
INCOME AND OUTGO OF ENERGY IN THE BODY. 
These experiments compare the amounts of potential energy 
in the materials actually oxidized in the body with the amounts 
of kinetic energy given off from it, either as heat alone in the 
rest experiments or as heat and external muscular work in the 
work experiments. 
In the rest experiments there was no considerable amount 
of external muscular work. The little that was done would 
naturally be converted into heat—as, for instance, in the im- 
pact of the foot upon the floor in stepping, or of the body upon 
the chair or bed in sitting or lying down. The heat thus im- 
parted tothe floor, chair, or bed would naturally find its way 
to the heat absorbers, and would thus be carried out with the 
heat given off as such by the body. Roughly speaking, we 
: may say that all the potential energy made kinetic in the body 
by the oxidation of food and body material left the body as 
heat, and that this made the net outgo of energy. | 
In the work experiments a certain amount of energy is given 
off as external muscular work, and this added to the heat given 
_ off from the body makes the net outgo. 
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