I NFL UENCE OF MUSC ULAR A CTIVIT Y. 715 
Analyses of the gases of blood taken from an animal after voluntary 
or involuntary muscular exertion show an increase in the oxygen and a 
decrease in the carbon dioxide. 
Gases of the Arterial Blood. 
Oxygen 
Volumes Pee Cent. 
Carbon Dioxide 
Volumes Per Cent. 
Animal. 
Rest. 
Activity. 
Rest. 
Activity. 
17-58 
17-33 
15-88 
17-68 
More than 16-04 
38-57 
36-49 
53-71 
35-01 j 
39-06 
Dog. 
Rabbit. 
Further, if the aorta be compressed in order to shut out the blood 
from the stimulated limbs, no hyperpncea is caused by the muscular 
activity ; section of the vagi, sympathetic and recurrent nerves, or 
section of the cord high up, does not prevent the stimulating effect of 
muscular exertion upon the respiratory centre. In rabbits the alkalinity 
of the blood is diminished by the acid formed during tetanic muscular 
activity, and this is probably a cause of the decrease in the carbon 
dioxide of the blood. No alteration could be found in the tension of the 
oxygen and carbon dioxide present hi the blood removed from an 
animal after muscular exertion. 1 
Lehmann 2 has shown that the injection of normal solution of 
tartaric acid stimulates and quickens the respiration of a rabbit, whereas 
a normal solution of sodium hydrate depresses the respiratory centre. 
According to Lowy's 3 experiments, the unknown substance which 
stimulates the respiratory centre during muscular activity is not 
excreted by the kidneys, and is not carbon dioxide ; for whereas the rate 
of respiration is doubled by muscular work when the increase above the 
normal amount of carbon dioxide in the expired air is only 0'5 per cent., 
yet the same amount of dyspnoea can be produced during rest only by 
artificially raising the percentage of carbon dioxide to a much higher 
point, about 5 per cent. 
The credit of the discovery that work is associated with an increase 
in the respiratory exchange, is due to Lavoisier, 4 who, in a series of 
experiments with Seguin, found that a man at work absorbed 9T2 
grms. of oxygen in an hour, whereas at rest he only absorbed 38*3 
grins. Although Vierordt 5 and Scharling 6 both observed a similar 
increase in the output of carbon dioxide in men at work, the first 
series of careful experiments on the subject were those performed by 
1 For criticism see Speck, DeutschesArch.f. klin. Med., Leipzig, 1891, Bd. xlvii. S. 509 ; 
for reply by Zuntz and Geppert, ibid., 1891, Bd. xlviii. S. 444. 
2 Arch./, d. gcs. Physiol., Bonn, 1888, Bd. xlii. S. 284. 
3 Ibid., S. 281 ; 1890, Bd. xlvii. S. 601. 
4 Hist. Acad. roy. d. sc, Paris, 1789, p. 185 ; "(Euvres de Lavoisier," tome ii. pp. 688- 
696. 
5 " Physiol, des Athmens," Karlsruhe, 1845; Arch. f. physiol. Heilk., Stuttgart, 
Bd. iii. S."536 ; Wagner's " Haudworterbuch d. Physiol.," 1844, Bd. ii. S. 828. 
6 Ann. d. Chan. u. Pharm., 1843, Bd. xlv. S. 214 ; Journ. f. prakt. C'hem., Leipzig, 
Bd. xlviii. S. 435. 
