The composition of the feces in the experiments here reported is 
shown in the table which follows. The composition of the urine and 
the respirator}- products is shown in connection with the tabular 
details of the individual experiments: 
Table 4. — Composition of feces in metabolism experiments Nos. 11, 13, 14, 21, 
26, 28, 29, 31, 32, and 34- 
24, 25, 
Laboratory No. 
Experi- 
ment 
No. 
Nitro- 
gen. 
Car- 
bon. 
Hydro- 
gen. 
Water. 
Pro- 
tein 
(Nx 
6.25). 
Fat. 
Carbo- 
drates. 
Ash. 
Heat of 
combus- 
tion per 
gram, 
deter- 
mined. 
2850 
11 
13 
14 
21 
23 
24 
25 
26 
28 
29 
31 
32 
34 
Per ct. 
1.59 
1.49 
1.57 
1.62 
1.59 
1.45 
1.38 
1.38 
1.70 
1.44 
1.52 
1.21 
1.38 
Per ct. 
14.30 
15.04 
13.49 
14.03 
14.44 
11.64 
13.73 
11.98 
13.61 
14.13 
15. 19 
12.87 
13.56 
Per ct. 
1.98 
2.14 
1.85 
1.94 
2.07 
1.65 
2.02 
1.44 
1.83 
2.03 
2.13 
1.86 
1.93 
Per ct. 
70.6 
69.8 
74.2 
72.6 
69.3 
75.7 
69.0 
72.3 
70.6 
69.9 
67.5 
73.2 
70.3 
Per ct. 
9.9 
9.3 
9.8 
10.1 
9.9 
9.1 
8.6 
8.7 
10.6 
9.0 
9.5 
7.6 
8.6 
Per ct. 
6.4 
8.3 
6.7 
6.3 
5.2 
4.9 
3.8 
3.6 
5.5 
5.1 
5.1 
4.5 
5.8 
Per ct. 
8.8 
7.0 
5.8 
6.3 
8.5 
5.4 
11.1 
8.5 
7.3 
10.3 
11.3 
9.6 
9.1 
Per ct. 
4.3 
5.6 
3.5 
4.7 
7.1 
4.9 
7.5 
6.9 
6.0 
5.7 
6.6 
5.1 
6.2 
Calories. 
1.554 
2965 
1.689 
2974 
1.500 
3033 
1.571 
3035 
1.610 
3036 
1.282 
3171 
1.571 
3183 
1.340 
3185 
1. 525 
3195 
1.574 
3197 
1.698 
3209 
1.449 
3211 
1.475 
DETERMINATION OF NITRATES AND NITRITES IN THE WATER 
OF RESPIRATION. 
Defren a calls attention to the presence of nitrates, and especially 
nitrites, in water of exhalation, and suggests the possibility of the 
nitrogen thus given off being sufficient in amount to take into account 
in studying the metabolism of nitrogen. 
It is of great importance in experiments of the nature of these, in 
which the balance of income and outgo of nitrogen is determined with 
great care, to take account of any nitrogen which might thus be 
eliminated. Since in the experiments here reported the products of 
respiration are passed through a refrigerating system and cooled to a 
temperature of about —20° C, there is excellent opportunity for a 
study of this subject. Accordingly, in several of the experiments, 
and more particularly in work experiment No. 6, already reported. b 
the water condensed in the 4i freezers" was carefully preserved and 
tested qualitatively for both nitrates and nitrites. The water con- 
densed from the incoming air was tested in a similar manner. Similar 
tests were also made of the water condensed on the surface of the 
absorbers and collected thence as "drip." 
■Technology Quarterly, 9 (1896), p. 238. See also Experiment Station Record, 8, 
p. 385. 
b U. S. Dept. Agr., Office of Experiment Stations Buls. 63, pp. 77-85; 69, pp. 
47-60. 
