RE8PIRA '/'/ox 133 



tion of C0 2 diminishes with the rise of external temperature from 4.4° until 



the temperature reaches 14.3°, when it rises slowly. Those results have been 

 substantiated by the more recent investigations of Page, 1 who found in experi- 

 ments on dogs that the discharge of C0 2 was at a minimum at about 2o° ; 

 that below this temperature the quantity increased as the temperature fell; 

 ami that above this temperature the discharge increased, and became greatly 

 augmented at temperatures of 40° to 42°. At the latter temperatures the 

 increase may reach Sh times the normal, but the bodily temperature is also 

 increased. If the elimination of C0 2 at 23° to 24° be represented by 100 as 

 a standard, at 13° it will be about 128; at 10°, 141 ; and at 8°, 177. The 

 researches of Speck, 2 of Loewy, 3 of Quinquaud, 4 and of Johansson 5 all show 

 that external cold increases respiratory activity, chiefly or solely by causing 

 involuntary muscular excitement (shivering). If shivering and other forms 

 of muscular activity be absent, the exchange of O and C0 2 is unaffected or even 

 diminished, but when present the increase of respiratory activity may amount 

 to 100 per cent, notwithstanding a fall of bodily temperature below the normal. 

 Muscular activity is one of the most important of all the circumstances 

 affecting the quantities of O and C0 2 exchanged. Involuntary excitement, 

 such as shivering, may of itself double the consumption of O and increase 

 two and a half times the elimination of C0 2 , but volitional muscular effort 

 may increase the interchange even beyond these limits. Hirn, in investiga- 

 tions on four men, noted during rest an hourly absorption of 30.2 grams of 

 O, and during work 120.9 grams; and Pettenkofer and Voit, in similar 

 studies, found an increase of O from 867 grams during rest to 1006 grams 

 during moderate work, and from 930 grams of C0 2 to 1137 grams. In 

 experiments on the horse Zuntz and Lehmann 6 obtained the following 

 results, which show to what a marked extent the respiratory interchange 

 may be increased by muscular activity : 



Liters per Minute. 



COj 



o 



O. CO, 



Kesting 1.722 1.570 0.92 



Walking 4.766 4.342 0.90 



Trotting 8.093 7.516 <>.'.':; 



Speck 7 has added some interesting facts to our knowledge of the effects of 

 muscular activity on the respiratory interchange. Thus, he found that the 

 increase of O and CG 2 reaches a maximum before exertion reaches its maxi- 

 mum ; that the increase for the same amount of work can be varied by chang- 

 ing the position of the body; that if a given amount of work be divided into 

 two equal parts, the increase of respiratory activity during the first period is 

 greater than during the second ; that the greater the increase of ( '< >,. the less, 



i Journal of Physiology, 1879-80, vol. 2, p. 228. 2 Lor. at. 



1 Archiv fur die gesammte Physiologie, 1890, Bd. 46, S. 189-224. 

 * Oompies rendvs, 1887, t. 104, pp. 1542 1544 



5 Skandinavisches Archiv fur Physiologie, 1897, Bd. 7, S. 123-177. 



6 Journal of Physiology, 1890, vol. 2, p. 396. 



7 Deutsche* Archiv f. Win. Med., 1889, Bd. 45, S. 460-528. 



Vol. I.— 28 



