WORK AND GAS EXCHANGE. 927 



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 l have made important investigations on 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 2 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. 



The quantity of carbon dioxide eliminated during a working period 

 is uniformly greater than the quantity of oxygen taken up at the same 

 time, and hence a raising of the respiratory quotient was usually con- 

 sidered as caused by work. This rise does not seem to be based upon the 

 character of the chemical processes going on during work, as we have a 

 series of experiments made by ZUNTZ and his collaborators, LEHMANN, KA'T- 

 ZENSTEIN and HAGEMANN, S in which the respiratory quotient remained 

 almost wholly unchanged in spite of work. According to LoEWY 4 the 

 combustion processes in the animal body go on in the same way in work 

 as in rest, and a raising of the respiratory quotient (irrespective of the 

 transient change in the respiratory mechanism) takes place only with 

 insufficient supply of oxygen to the muscles, as in continuous fatiguing 

 work or excessive muscular activity for a brief period, also with local 

 lack of oxygen caused by excessive work of certain groups of muscles. 

 This varying condition of the respiratory quotient has been explained by 



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

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

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

 Zuntz and Hagemann, Berlin, 1898; Hohenklima und Bergwanderungen by Zuntz, 

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



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

 des menschl. Atmens," Leipzig, 1892. 



3 See footnote 1. 



4 Pfliiger's Arch., 49. 



