NET AVAILABLE ENERGY—MAINTENANCE. 401 
tion for the four days of each experiment (excluding preliminary 
feeding) is computed from the proteid metabolism as measured 
by the urinary nitrogen, on the assumption that all the fat con- 
tained in-the meat and all the non-nitrogenous nutrients added 
were -metabolized. An exception is made in the fourth period, ’ 
however, in which the author computes from a comparison of the 
. gains of nitrogen and of live weight that there was a gain of about 
50 grams (?) of fat by the animal. The results are contained in 
the first six columns of the following table: 
Gain or Loss of Esti- Cor- 
Gain or mated | rected 
cd Loss of Heat | Heat 
8 Food. Weight, | wit Equivalent | Pro- | Pro- 
5 Grms. : Great Flesh, |duction,|duction, 
fy . Grms. Cals. Cals. 
I | 1000 grms. mea aan’ | —895 +19.39 | +570 4548 | 6190 
500 ete 
II 40 “ jad Cae —170 — 1.86} — 55 3903.} 4981 
ad ss a ee 1.81 | + 53 | 5326 | 5354 
80 “ lard..... 
FE 
+ 
v4 a ms +335 (| + 6.36 | +187 (| 5486 | 4566 
Vv 500 ‘“ meat.... a: 
| om se | 
{ 100 “ gelatin ot 
+152 6.04 | +170 3811 | 3980 
VI —~105 | —1.10| —.32 | 4088 | 4773 
Making the comparison of fat and carbohydrates, as the essen- 
tial point, it would appear from Contejean’s results that 100 grams 
of sugar was fully as efficient as 80 grams of fat, while according 
to Rubner’s figures about 180 grams of sugar would be required. 
Corresponding to this is the lower computed heat production in the 
sugar period, the excess in the fat periods being ascribed to the 
cleavage of fat believed to occur in the liver. 
If, however, there is justification for computing the gain of fat 
by the body in the fourth period by subtracting the gain of flesh 
from the total gain in weight, the same method is equally applicable 
to the other periods. By its use the figures of the last column of 
the table have been computed by the writer. While the heat 
production in the sugar period as thus estimated is still below that 
of. the fat periods, the rather wide range in the results of the latter 
serves to illustrate the uncertainties of such computation. 
