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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
cl.aracter of the chemical processes going on during work, as we have a
series of experiments made by Zuntz and his collaborators, Lehmann, Kat-
zenstein and Hagemann,3
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 cf 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’a 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.
^ord. 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.
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