EXPERIMENTS ON METABOLISM OF ENERGY. Vthin 
One point, however, is so interesting that a word regarding 
it may be in placé here. Comparisons of the figures for 
amounts of hydrogen oxidized, as given in the tabular details 
of the experiments, show that if all the water formed by the 
oxidation of the hydrogen of the food and body material were 
eliminated through the lungs and skin, and none through the 
kidneys, it would account for only about one-third of the water 
of respiration and perspiration in the rest experiments, and 
only about one-fourth of that in the work experiments. It is 
therefore evident that the increase of water of respiration and 
perspiration during periods of muscular activity is due not so 
much to an increased oxidation of hydrogen as to an increased 
excretion through the lungs and skin of water from some other 
source. 
The amounts of water eliminated by the lungs and skin in 
the different periods of the day as compared with the day as a 
whole are shown in Table 26. 
In the rest experiments with E. O. the total amount of 
water of respiration and perspiration ranged from 697 to 1,143, 
and averaged 948 grams per day. Comparing the twelve hours 
of the day with the twelve hours of the night, the amounts of 
water eliminated were practically the same, being, respectively, 
49.5 and 50.5 per cent. of the whole. | Comparing by periods, 
the largest elimination, 42.6 grams per hour, was in the first, 
and the smallest 37.3 grams per hour, in the last of the night 
periods, but the differences in the different periods were not 
large. ‘The amounts with A. W. S. were somewhat smaller, 
the average daily elimination being 859 grams. Here again it 
was equally divided between the day and the night, and the 
amounts in the six-hour periods differed but little, although 
the amount in the first night period was slightly larger than 
that in the second night period, the latter being little smaller 
than in either of the day periods, as was the case with E. O. 
The average daily elimination with J. F. S., 830 grams, was 
still less than with A. W. S. In this case the elimination was 
somewhat larger during the day than during the night periods, 
being 52 per cent. of the whole for the former as compared with 
48 per cent. for the latter. The average for both the day per- 
iods was the same, 36.0 grams. As was the case with the 
two other subjects, the average for the first night period was 
