NITROGEN CATABOL1SM 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 HrascHFELD, 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 (Munchen, 1860), and Zeitschr. f. Biologic, 

 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. Fimke, Kellner, cited from Voit, Hermann's Handb., 86, 197; Dunlop 

 Noel-Paton, Stockman, and Maccadam, Journ. of Physiol., 22; Krummacher, Zeitschr. 

 f. Biologic, 33; Pfliiger, Pfluger's Arch., 50; Zuntz, Arch. f. (Anat. u.) Physiol., 1894. 



3 Engelmann, Arch. f. (Anat. u.) Physiol., 1871; Beck and Benedict, Pfluger's 

 Arch., 54, and also footnote 2. 



4 Caspari, Pfluger's Arch., 83; Bornstein, ibid.; Kaup, Zeitschr. f. Biologic, 43; 

 Wait, U. S. Depart. Agricult. Bulletin, 89; (1901) Atwater and Benedict, ibid., Bull., 

 69 (1899); Loewy.Arch. f. (Anat. u.) Physiol., 1901. 



