566 MUSCLES. 



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 therefore 

 also a measure of the protein catabolism. The earlier researches of ENGEL- 

 MANN, FLINT, and PAVY, as well as the more recent ones of BECK and 

 BENEDICT, 3 and DUNLOP and his collaborators, show an increased elimina- 

 tion of sulphur during or after work, and this indicates an increased pro- 

 tein 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/ that a retention of nitrogen 

 and a exposition of protein occur during work. The discordant 

 observations 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 

 and composition of the food, the condition of the adipose tissue of the 

 body, the action of the work upon the respiratory mechanism, etc., all 

 of which have an influence on the results of the experiments. 



Recently STEYRER 5 has found that the muscle juice of a continuously tetani zed 

 muscle was somewhat poorer in musculin and correspondingly richer in myogen 

 than the juice from a similar non-tetanized muscle. We cannot draw any con- 



1 Voit, Untersuchungen iiber den Einfluss des Kochsalzes, des Kaffees und der 

 Muskelbewegungen auf den Stoffwechsel (Mimchen, 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, 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, Pfliiger's Arch., 83; Bornstein, ibid.; Kaup, Zeitschr. f. Biologie, 43; 

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

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



5 Hofmeister's Beitrage, 4. 



