PHYSIOLOGICAL EFFECTS 171 
In very few instances was the oxygen consumption per minute less than 10 
per cent above normal when the observations ceased each day; particularly 
is this true for experiments with M. A. M. after January 2, 1912. On some 
days, when these measurements were carried out for 2 to 4 hours, an increase 
in the metabolism of 14 or 15 per cent has been repeatedly noted at the end 
of the observations. The one exception to this is the experiment of April 16, 
1912, in which the metabolism apparently reached its normal level in 1 hour 
and 20 minutes after the work ceased, but in relatively few of the experiments 
does the oxygen consumption finally reach the base-line before the experiment 
terminates. Here again, however, since these observations were wholly 
subsidiary to the major problem studied, we could not hold the bicyclist in 
the laboratory an undue length of time to obtain further fight on this m i nor 
question. 
The values given in table 136 for the experiments with H. L. H., and 
E. P. C, as well as for a few of the experiments with M. A. M., imply that the 
after-effect of muscular work is but little greater than that given by Loewy, 
namely, that the total excess oxygen consumption following work is approxi- 
mately the same as for 1 minute of hard work. This general deduction does 
not hold true, however, for practically all of the experiments with the subject 
M. A. M. after January 2, 1912. That the results of our earlier experiments 
are not far from, although they actually do exceed Loewy's estimate, can be 
shown by the following computation: Using the low values given for January 
2, we find that the observations for the first period of rest began 10 minutes 
after the work ended and continued for the usual 15-minute period. Assum- 
ing the increase during the first 10 minutes after the work to be no greater 
than that found during the first period of rest, i. e., 39 c.c. per minute, there 
would be in the first 25 minutes after the work ceased an increased consump- 
tion of oxygen of 39 c.c. per minute, or a total excess amount of 975 c.c. 
An intermission of 9 minutes was followed by a second rest-period of 17 
minutes; in this second rest-period the excess oxygen consumption was 25 c.c. 
per minute, and although during the intermission it was doubtless a little 
higher, we may assume that for the 26 minutes of intermission and rest-period 
the increase was constant, so that the total excess amount was 650 c.c. 
This added to the 975 c.c. computed for the first 25 minutes after the work 
ceased gives us 1,625 c.c. as the excess oxygen consumption in the 51 minutes 
following the cessation of work. On the assumption that no further incre- 
ment in the oxygen consumption took place, it will be seen that this corre- 
sponds to a consumption of oxygen approximately 25 per cent larger than 
that during 1 minute of the last period of work, i. e., 1,244 c.c. (See table 136.) 
It should be remembered that this particular experiment was chosen as show- 
ing one of the lowest increases due to the muscular activity. 
Bearing in mind the sharp gradient in the oxygen consumption which 
must take place immediately after the work ceased, it can be seen that in 
practically every experiment not only does the muscular work greatly increase 
the average oxygen consumption and heat output in the following periods, 
but this effect is long continued. Since it has been shown that the increase 
cannot be attributed to the mechanical work of an increase in the ventilation 
of the lungs, we have here unquestionably a sustained high metabolism due 
to the previous muscular exercise. How long this effect would continue, 
