868 METABOLISM. 



prevailing sentiment is that muscular activity has hardly any influence 

 on the metabolism of proteins. 



On the contrary, work has a very considerable influence on the elimina- 

 tion of carbon dioxide and the consumption of oxygen. This action, 

 which was first observed by LAVOISIER, has later been confirmed by 

 many investigators. PETTENKOFER and VOIT 1 have made investiga- 

 tions on a full-grown man as to the metabolism of the nitrogenous as well 

 as of the non-nitrogenous bodies during rest and work, partly while 

 fasting and partly on a mixed diet. The experiments were made on a 

 full-grown man weighing 70 kilos. The results are contained in the 

 following table: 



Consumption of 

 Proteins. Fat. Carbohydrates. CO 2 Eliminated. O Consumed. 



-P ,. / Rest 79 209 ... 716 761 



nng- ^ Work 75 380 . 1187 1071 



Mixed diet / Rest 137 72 352 912 831 



' { Work 137 173 352 1209 980 



In these cases work did not seem to have any influence on the destruc- 

 tion of proteins, while the gas exchange was considerably increased. 



ZUNTZ and his pupils 2 have made important investigations into 

 the extent of the exchange of gas as a measure of metabolism during 

 work and caused by work. These investigations not only show the impor- 

 tant influence of muscular work on the catabolism of material, but they 

 also indicate, in a very instructive way, the relation between the extent 

 of metabolism of material and its utilization for work of various kinds. 

 We can refer only to those which are of special physiological interest. 



The action of muscular work on the gas exchange does not alone appear 

 with hard work. From the researches of SPECK and others we learn that 

 even very small, apparently quite unessential movements may increase 

 the production of carbon dioxide to such an extent that by not observing 

 these, as in numerous older experiments, very considerable errors may 

 creep in. JOHANSSON 3 has also made experiments upon himself, and 

 finds that on the production of as complete a muscular inactivity as 

 possible the ordinary amount of carbon dioxide (31.2 grams per hour 

 at rest in the ordinary sense) may be reduced nearly one-third, or to an 

 average of 22 grams per hour. 



1 Zeitschr. f . Biologie, 2. 



2 See the works of Zuntz and Lehmann, Maly's Jahresber., 19; Katzenstetn, Pfliiger's 

 Arch., 49; Loawy, ibid.', Zuntz, ibid., 68, Zuntz and Slowtzoff, ibid., 95; and especially 

 the large work " Untersuch. uber den Stoffwechsel des Pferdes bei Ruhe und Arbeit," 

 Zuntz and Hagemann, Berlin, 1898; Hohenklima und Berg wand erungen by Zuntz, 

 Loewy, Miiller and Caspan, which also contains a bibliography. 



3 Nord. Med. Arkiv. Festband, 1897; also Maly's Jahresber., 27; Speck, " Physiol. 

 des menschl. Atmens," Leipzig, 1892. 



