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NITROGEN CATABOLI8M IN ACTIVE MUSCLES. 595
activity by determining the total quantity of nitrogen eliminated under
these different conditions of the body. While formerly it was held with
Liebig that the elimination of nitrogen by the urine was increased by
muscular work, the researches of several experimenters, especially those
of Voit on dogs, and Pettenkofer and Voit on men, have led to quite
different results. They have shown, as has also lately been confirmed
by other investigators, especially I. Munk and Hirschfeld,1
that during
work no increase, or only a very insignificant increase, in the elimination
of nitrogen takes place.
We should not omit to mention the fact that a series of experiments
has been made showing a significant increase in the metabolism of pro-
teins during or after work. There are for example the observations
of Flint and of Pavy on a pedestrian, v. Wolff, v. Funke, Kreuzhage,
and Kellner on a horse, and Dunlop and his collaborators on working
human beings, and of Krummacher, Pfluger, Zuntz and his pupils,2
and others. The researches on the elimination of sulphur during rest
and activity also belong to this category. The elimination of nitrogen
and sulphur runs parallel with the metabolism of proteins in resting and
active persons, and the quantity of sulphur excreted by the urine is there-
fore also a measure of the protein catabolism. The earlier researches
of Engelmann, Flint, and Pavy, as well as the more recent ones of Beck
and Benedict,3
and Dunlop and his collaborators, show an increased
elimination of sulphur during or after work, and this indicates an increased
protein metabolism because of muscular activity.
That an increased destruction of protein is not necessarily produced
by work follows from the observations of Caspari, Bornstein, Kaup,
Wait, A. Loewy, Atwater and Benedict,4
that a retention of nitrogen
and a deposition of protein occur during work. The discordant observa-
tions on the protein destruction during, and caused by, work are not
directly in opposition to each other, because the extent of protein
metabolism is dependent upon many conditions, such as the quantity
1
Voit, Untersuchungen iiber den Einfluss des Kochsalzes, des Kaffees und der
Muskelbewegungen auf den Stoffwechsel (Miinchen, 1860), and Zeitschr. f. Biologie,
2; J. Munk, Arch. f. (Anat. u.) Physiol., 1890 and 1896; Hirschfeld, Virchow’s Arch.,
121.
2
Flint, Journ. of Anat. and Physiol., 11 and 12; Pavy, The Lancet, 1876 and 1877;
v, Wolff, v. Funke, Kellner, cited from Voit, Hermann’s Handb., 86, 197; Dunlop
Noel-Paton, Stockman, and Maccadam, Journ. of Physiol., 22; Krummacher, Zeitschr.
f. Biologie, 33; Pfluger, Pfliiger’s Arch., 50; Zuntz, Arch. f. (Anat. u.) Physiol., 1894.
3
Engelmann. Arch. f. (Anat. u.) Physiol., 1871; Beck and Benedict, Pfliiger’s
Arch., 54, and also footnote 2.
"Caspari, Pfluecr’s Arch., 83; Bornstein, ibid.; Kaup, Zeitschr. f. Biologie, 43;
Wait, U. S. Depart Agricult. Bulletin, 89; (1901) Atwater and Benedict, ibid., Bull.,
69 (1S99); Loewy, Arch. f. (Anat. u.) Physiol., 1901.
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