100 MUSCULAR WORK 
somewhat less than that found by Benedict and Carpenter in resting experi- 
ments with a large number of normal subjects." It is thus obvious that dur- 
ing the actual time of work there was not an excessive excretion of nitrogen 
per hour. This is further shown by the data for March 18 and April 8 with 
M. A. M., when the subject worked nearly the whole period of collection, 
the nitrogen excretion being about the same as in periods covering rest and 
work. On the other hand the figures throw absolutely no light upon the 
lag in the excretion of nitrogen following severe muscular work which has 
been observed by many investigators. 
So much experimental evidence has already been accumulated to prove 
that protein cannot be the sole source of muscular work that no further at- 
tempt was made with our professional subject to collect the urine throughout 
the day, especially as this was difficult inasmuch as after the work was over 
each day he left the laboratory and the greater part of the time was uncon- 
trolled as to diet. The data given in this table are interesting only in showing 
that even after the excessively severe work frequently done by the subject 
M. A. M. there was, on the whole, no great increase in the excretion of nitro- 
gen from the body. 6 
On the other hand it should be stated that the volumes of urine were 
for the most part very small. There was very free perspiration and hence the 
fluid excreted by the kidneys was reduced to a minimum. In one case but 
50 c.c. of urine could be collected, while from 7 o'clock until 12 o'clock noon 
of another experimental day but 26 c.c. of urine were secured; in at least one 
instance (February 1) the subject was unable to pass any urine. It is thus 
obvious that with such fragmentary evidence as this no sweeping conclu- 
sions can be drawn, but that experiments planned primarily to study this 
problem are necessary in order to secure data that can be of material use. 
The values for nitrogen were secured primarily for the purpose of supplying 
data to be used in conjunction with the measurements of the gaseous exchange 
for computing the amounts of protein, fat, and carbohydrate katabolized — 
a computation frequently employed by many writers. On the other hand 
it should be stated that in all probability it is entirely erroneous to assume 
that the nitrogen excretion is coincidental with the metabolism of protein, 
as the excretion of abnormally large amounts of nitrogen are frequently 
observed after severe muscular work, showing that there is a distinct delay 
in the excretion of the decomposition products of protein. Although it has 
been pointed out that if any increase in nitrogen output takes place following 
work it usually appears two to three days afterwards, this is in the present 
series of experiments of little moment as the majority of the actual tests 
were carried out on consecutive days. 
a Reported by Benedict and Joslin, Carnegie Institution of Washington Publication No. 176, 1912, p. 103. 
6 Fragmentary evidence bearing on this point has been secured in this laboratory on Marathon runners which 
shows that the total nitrogen output per hour during the severe work of running was small. See Rig- 
gins and Benedict, Am. Journ. Physiol., 1911, 28, p. 291. 
