382 INFLUENCE OF MUSCULAR CONTRACTION ON RESPIRATION. [BOOK I. 



respiration is enlarged both during and immediately after the period 

 of exercise 1 . 



But the variations of the carbon dioxide exhaled and the oxygen 

 absorbed do not occur pari passu ; the relationship of rest is 

 different from that of activity. The exact determination of this 

 relationship, although theoretically very simple, is a matter of 

 considerable practical difficulty ; and the gradual improvement of the 

 apparatus employed may be traced in the series of papers already 

 referred to. No attempt will be made here to explain the practical 

 methods, inasmuch as the classical apparatus of Regnault and Reiset' 2 , 

 Sczelkow 3 and Pettenkofer and Voit 4 , will be described in the Chapter 

 on Respiration. The object of all the improved appliances is to 

 exactly estimate the oxygen absorbed, and the carbon dioxide excreted, 

 while the air entering the animal's lungs is of fairly normal constitution 

 and pressure. 



Methods of To effect this there are three chief methods. The 



Experiment. animal may be enclosed in an air-space disconnected 

 from the external air, the carbon dioxide being removed, and the 

 oxygen being replaced, as they are formed and consumed respectively 

 (Regnault et Reiset). Or the animal may be made to breathe out of 

 one vessel and into another, the loss and gain respectively being 

 accurately measured, while the pressure in each vessel is maintained, 

 by suitable apparatus, the equal of that of the atmosphere (Sczelkow). 

 Or the animal may be kept in a space through which air is continually 



1 Among those who discovered and investigated the influence of muscular exercise 

 upon the exchanges of respiration may be mentioned the following : Jurine, quoted in 

 the Encyclopedie methodique, Art. "Medecine," Vol. i. p. 494: ed. by Vicq. D'Azyr, 

 1787. Seguin et Lavoisier, "Premier Memoire sur la Respiration des animaux." 

 Mem. Acad. 1789, p. 575. Other researches of Lavoisier will be referred to under 

 ' Respiration.' W. Prout, "Observations on the quantity of carbonic acid gas emitted 

 from the lungs during respiration." Thompson's Annals of Philosophy, Vol. n. 1813, 

 p. 328. Translated into Schweigger's Journal fur Chemieu. Physik, 1815, Vol. xv. p. 47. 

 E. A. Scharling, " Dritte Reihe der Versuche um die Menge der Kohlensaure zu 

 bestimmen welche vom Menschen in einen gewissen Zeit ausgeathmet wird." Journal 

 fur prakt. Chemie, Vol. XLVIII. 1849, p. 440. Vierordt, Physiologic des Athmens. 

 Andral et Gavarret, "Recherches sur la quantity d'acid carbonique exhale par le 

 poumon dans 1'espece humaine." Ann. de Chimie et de Physique, Ser. in. Vol. vui. 

 1843, p. 129. Regnault et Reiset, "Recherches chimiques BUT la Respiration des 

 animaux des diverses classes." Ann. de Chimie et de Physique, Ser. in. Vol. xxvi. 

 1849, p. 299. Ed. Smith, "Experimental Inquiries into the phenomena of Respiration." 

 Trans. Roy. Soc. Lond. 1859, Vol. CXLIX. pt. ii. p. 681. Pettenkofer und Voit, 

 "C0 2 -Ausscheidung u. 0-Aufnahme wahrend des Wachens u. Schlafens." Sitzungsber. der 

 fc. hayer. Akad. d. Wissensch. zu Miinchen, 1866, Vol. u. p. 236. Ibid. 1867, Vol. i. p. 255. 

 Speck, Schriften d. Gesellsch. z. Be/order, d. ges. Naturwissensch. zu Marburg, Vol. x. p. 3, 

 1871. Rohrig und Zuntz, "Zur Theorie der Warrneregulation und Balneotherapie " 

 Pfluger's Archiv f. d. ges. Physiol. Vol. iv. p. 57. Zuntz, "Ueber den Einfluss der 

 Curarevergiftung auf den thierischen Stoffwechsel." Pfluger's Arch. Vol. xn. p. 522. 



2 Regnault et Reiset, " Recherches chimiques sur la Respiration des animaux des 

 diverses classes." Ann. de Chimie et de Physique, 3rd series, xxvi. p. 299, 1849. 



3 Sczelkow, Op. cit. 1862. 



4 Pettenkofer, "Ueber einen neuen Respirations- Apparat. " Abhandlunr/en der matli.- 

 phys. Classe d. k. layer. Akad. d. Wiss. Vol. ix. Miinchen, 1863, p. 229. Voit, "Beschrei- 

 Ijung eines Apparates zur Untersuchung der gasformigen Ausscheidungen des Thier- 

 korpers." Ibid. Vol. xn. Miinchen, 1876, Abth. i. p. 219. 





