INFLUENCE OF MUSCULAR EXERTION UPON METABOLISM. 215 
no mention is made of the nature of the diet except in one case 
(fasting). The individual results were rather variable, but most 
weight is given to those on Subject No. 1, with whom most of the 
experiments were made. Katzenstein believes Speck’s results to 
be due in part to a change in the rate of respiration, causing the 
excretion of carbon dioxide to exceed its actual production (p. 73), 
and in part to a deficiency of oxygen in the tissue of the contracting 
muscles. 
Loewy,* like Katzenstein, found that work pushed to the point 
of producing a considerable degree of fatigue raised the respiratory 
quotient, while moderate work did not. Rapid turning of the 
wheel of the ergostat, preventing full breathing, or compression 
of the upper arm by means of a rubber band, produced the same 
effect, which he attributes to a lack of oxygen. The most marked 
results seem to be those for the first few minutes of work, although 
in one case work continued for ten to twenty minutes and producing 
fatigue raised the respiratory quotient. 
Probably the most extensive and carefully conducted investiga- 
tions of this nature are those of Zuntz and his associates upon the 
dog, and particularly on the horse. Some data from the latter 
investigations have already been given on p. 212. The following 
table adds to the averages there quoted those for the corre- 
sponding rest periods. In these experiments there was a distinct 
lowering of the respiratory quotient instead of an increase. In 
v 
Respiratory Quotient. 
Kind of Work. Periods. 
Repose. Work. 
Walking nearly horizontal........... a, b, e, f,t,0 0.943 0.865 
se up slight grade............. a, b, e, 0 0.940 0.847 
ee “ steeper grade. : ...| u,b, ef, tn 0.953 0.900 
Draft, nearly horizontal.............. b, e, f,% 0.956 0.890 
Walking with load, nearly horizontal... e, t, 0 0.915 0.840 
“ up a grade................. €,1, O,u 0.915 0.893 
Trot, nearly horizontal a, €, f, 0 0.943 0.882 
ee « @, 1, 0 0.915 | 0.873 
“ horizontal, with draft 9,f,% 0.943 0.927 
* Arch. ges. Physiol., 49, 405. 
