INFLUENCE OF MUSCULAR EXERTION UPON METABOLISM. 203 
days, sufficient to supply an amount of energy equal to that 
actually measured on the ergostat, so that at least the larger share 
of the energy must have been derived from non - nitrogenous 
materials. 
Zuntz & Schumburg,* in investigations upon soldiers, observed 
an increase of the proteid metabolism as the result of marching, 
carrying a considerable weight. The increase, however, seemed to 
bear no direct relation to the amount of work performed, but rather 
to the conditions under which it was done. Thus excessive heat or 
sultriness of the atmosphere, resulting in unusual fatigue, was ac- 
companied by an increased excretion of nitrogen. The increase 
continued during the two days following the work. 
Frentzel + experimented upon dogs. In the first series’the ani- 
mals were fed pure fat, while in the second series no food was given. 
The work, which was done upon a tread power, was considerable. 
In the first series there was an increase of 9.25 per cent. in the nitro- 
gen excretion in the work experiments, while in the second series a 
maximum increase of 44.26 per cent. was computed, which, how- 
ever, is believed by the author to be too high. A method of com- 
putation which he considers more nearly correct makes the increase 
in the second period 13.31 per cent. In the first series of experi- 
ments the food consisted of 150 grams of fat per day except upon 
one of the work days, when only 80 grams were consumed. No data 
are given regarding the sufficiency of this ration, but according to 
E. Voit’s compilation { it would appear hardly adequate for the 
maintenance of a dog of the weight used (36 kilograms). The work, 
therefore, even in the first series, was probably done upon insuf- 
ficient food. In neither case was the increase in the amount of 
protein metabolized equivalent in energy content to the actual 
amount of external work done, and in the first series even the total 
proteid metabolism was not, while if we allow for the consumption 
of energy in internal work, heat production, etc., it was not suf- 
ficient in either series. 
Atwater & Sherman § have reported observations upon the 
* Arch. f. (Anat.'u.) Physiol., 1895, p. 378. 
+ Arch. ges. Physiol., 68, 212. 
t Zeit. f. Biol., 41, 115 
§ U.S. Dept. Agr., Office of Experiment Stations, Bull. 98. 
