INFLUENCE OF MUSCULAR EXERTION UPON METABOLISM. 197 
mann, and was entirely insufficient to account for the energy ex- 
pended. Oppenheim made the interesting, observation that work 
pushed to the point of producing dyspnoea caused a marked increase 
in the proteid metabolism. 
INFLUENCE oF TotaL Amount oF Foop—KELLNer’s INvEs- 
TIGATIONS.~~Doubtless the conflicting results of earlier experiments 
are due in part to defective technique, but they arise in part also, 
as it would seem, from another cause to which attention was first 
called by Kellner in 1879-80. Kellner’s experiments were made 
upon the horse. They differed from most earlier experiments, first, 
in that the comparison was made between different amounts of work 
instead of between work and rest, and second, that the individual 
periods instead of covering only a few days were extended over two 
or three weeks. 
Sertes I.—Kellner’s first series * was made primarily for the 
purpose of testing the influence of work upon the digestibility of the 
food, but the total nitrogen of the urine was also determined. The 
methods employed for this purpose were somewhat imperfect, there 
being some mechanical loss and probably also a loss of ammonia 
from the urine, but the author believes the results of the several 
periods to be fairly comparable. The amount of work performed 
was measured by a dynamometer. The numerical results of the 
measurement have since been shown to be too high, but the relative 
amount in the several periods is not thought to be materially 
affected by this error. The results of the several periods are briefly 
summarized in the following table: 
Nitrogen. Live Weight 
, Work, at Close 
Period. Kem. of Period, 
Digested, In Urine, Kgs. 
Grms. Grms. 
1 ee ae ae EE eT 625,000 134.41 99.0 534.1 | 
LT iedae see vig KOE Roms 1,250,000 128 .32 109.3 529.5 
Tlie sens aanies eis cee 1,875,000 132.72 116.8 522.5 
PWocie oa 8 ex hase ea Se Rees 1,100,000 126.40 110.2 508.8 
IV cid Sedgeteie tenn SOG 8S OG 625,000 129.41 98.3 518.0 
While the above figures show a considerable nitrogen deficit, 
the urinary nitrogen increased and decreased with the amount of 
* Landw. Jahrb., 8, 701. 
