INFL UENCE OF MUSCULAR A CTIVITY. 7 1 5 



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. 



Further, if the aorta be compressed in order to shut out the blood 

 from the stimulated limbs, no hyperpnoaa 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 in the blood removed from an 

 animal after muscular exertion. 1 



Lehmarm 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 91 '2 

 grms. of oxygen in an hour, whereas at rest he only absorbed 38'3 

 grms. 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, Deutsches Arch. f. klin. Med., Leipzig, 1891, Bd. xlvii. S. 509 ; 

 for reply by Zuntz and Geppert, ibid., 1891, Bd. xlviii. S. 444. 



2 Arch.f. d. ges. 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 " Handworterbuch d. Physiol.," 1844, Bd. ii. S. 828. 



6 Ann. d. Chcm. u. Pharm., 1843, Bd. xlv. S. 214; Journ. f. prakt. Chem., Leipzig, 

 Bd. xlviii. S. 435. 



