123 
While none of these topics pan be discussed to the best advantage 
until the publication of further experimental data, or without due con- 
sideration of the results of research elsewhere, brief reference may be 
made to a few of them in order to illustrate some of the ways in which 
the experiments are throwing light upon the fundamental questions 
of the metabolism of matter and energy in the body, and consequently 
upon the general laws of nutrition. Accordingly, the data already 
reported are here used for a preliminary discussion of a number of 
problems of general interest. These include (1) food materials -up- 
plied and consumed and the difference in the amounts of nutrients 
demanded by men at rest and at work. (2) the elimination of water. (3) 
the elimination of carbon dioxid. (4) the elimination of energy, and 
(5) the income and outgo of energy and the action of the law of the 
conservation of energy in the body. The text-books and treatises bear- 
ing on these subjects contain more or less detailed statements and 
conclusions. It appears that in numerous instances the commonly 
quoted figures and conclusions rest upon much less experimental evi- 
dence than- is furnished by the experiments with the respiration calo- 
rimeter just referred to. In the construction of this apparatus it was 
possible to make use of the experience and results of earlier investi- 
gators; the facilities have permitted the obtaining of more accurate 
and extensive data than had previously been practicable: and it is 
believed that the results are of sufficient interest to warrant their 
publication even though future research may call for more or less modi- 
fication of the inferences deduced from them. 
Brief summaries of results are given on the following pages. These 
results are derived from the statistics of experiments Nos. 5-11. 13, 
14. 21. 23-26. 28, 29. 31. 32. and 34. The result.- summarized in 
Table 144. p. 129. include, in addition, the results of experiments 
Nos. 1-4. in which the outgo of energy was not determined. 
Subjects of the experiments. — Four different men. E. O., O. F. T., 
A. W. S... and J. F. S.. have served as subjects in these experiments. 
They were all in excellent health. E. O. was a laboratory assistant, 
a native of Sweden, who had been a number of years in this country. 
At the time of the experiments here recorded he was about 32 years 
old and weighed not far from 70 kilograms. A. W. S. was a phys- 
icist, a native of New England. 25 years old. and weighed about 70 
kilograms. O. F. T.. a chemist, the subject of but one experiment, 
No. 3. was also a native of New England. 24 years old. and weighed 
about 60 kilogram- J. F. S.. a chemist, was a native of Canada. 29 
years old. and weighed about 65 kilograms. 
Rest and work experiments. — In the rest experiments the subjects 
were as quiet a- they well could be. Practically their only muscular 
exercise was that involved in dressing and undressing, folding and 
