RESPIRATION. 



359 



and Tiedemann*, Stromeyerf, Mliller and 

 others J . failed in obtaining any carbonic acid 

 gas from the blood by the air-pump and other 

 means, and it was not until the publication of 

 the important experiments of Magnus, con- 

 firmed as they have been to a certain extent 

 by other observers, and strengthened by evi- 

 dence collected both before and since on the 

 results of the respiration of animals in hy- 

 drogen and nitrogen gases, that the existence 

 of any free gas in the blood has been gene- 

 rally admitted. Bertuch and Magnus pro- 

 cured carbonic acid gas from human venous 

 blood by agitating it with hydrogen.^ Mag- 

 nus has not only obtained carbonic acid gas 

 from both kinds of blood in some of the 

 domesticated animals, but also oxygen and 

 azote by means of the air-pump. The two 

 latter gases were also procured from both 

 kinds of blood by agitation with carbonic acid 

 gas. The quantity of gases obtained from 

 the blood by the air-pump in these expe- 

 riments by Magnus amounted to T Vt-h> and 

 sometimes to J-th of the volume of the blood 

 employed ; but from the difficulty of libe- 

 rating the gases from the blood, he believes 

 that this quantity forms but a small part of 

 that actually held in solution in this fluid. 

 In some experiments with hydrogen, the quan- 

 tity of carbonic acid obtained amounted to th 

 of the volume of the blood employed. The 

 relative quantity of oxygen gas to the car- 

 bonic acid gas is greater in arterial than in 

 venous blood. In venous blood the oxygen 

 was as^th, and often -tth, while in arterial blood 

 it was at least as id and sometimes i to the 

 carbonic acid.|| Magnus, in a second memoir 

 on this subject, states that he obtained the 

 following quantities of oxygen and nitrogen 

 from the arterial blood of two old horses, by 

 agitating it in carbonic acid gas : 



Oxygen. Azote. 



10'5 2-0 \ per cent, of the volume 



1 3-3 J of blood employed.^ 



By adding together the total quantity of gases 

 collected from each kind of blood in his dif- 

 ferent experiments by means of the air-pump, 

 and then comparing the relative proportions 



* Loc. cit. 



f Dissertatio Liberumne Acidum Sanguine, con- 

 tinetur. Gottingen, 1831. 



J Two at least of these experimenters, viz. Dr. 

 Davy and Gmelin, have since satisfied themselves 

 that carbonic acid gas is evolved from blood under 

 the air-pump. Dr. Davy (Philos. Transact, for 

 1838, p. 291) obtained it in small quantities both 

 from venous and arterial blood, and Gmelin (Preface 

 to BischofPs Commentatio de Novis quibusdam 

 Experimentis, &c.) also in small quantity from 

 venous blood. 



PoggendorfPs Annalen der Physik und Chemie, 

 Band xl. S. 583. 1837. 



|| Idem opus. 



^ PoggendorfFs Annalen, Band Ixvi. S. 202. 1845. 

 Enschut had, previous to Magnus's experiments, 

 obtained azote from both kinds of blood, and in 

 greater quantity from venous than from arterial 

 blood. Opus cit. p. 159. 



of their constituent parts, the following results 

 are obtained : 



The quantity of oxygen gas procured from 

 the blood of calves, oxen, and horses, pre- 

 viously agitated with atmospheric air, was not 

 less than 10 per cent, and not more than 12 

 per cent. The blood can, however, absorb a 

 greater quantity of oxygen and nitrogen than 

 was collected in the" experiments last-men- 

 tioned, for by repeatedly shaking blood with 

 renewed quantities of carbonic acid gas to 

 remove the whole of the oxygen and nitrogen 

 gases it contained, and then agitating it in 

 measured quantities of atmospheric air, he 

 ascertained, by again measuring the atmo- 

 spheric air. that the minimum quantity of 0x3- 

 gen absorbed amounted to 10 per cent., and 

 the maximum to 16 per cent. The quantity of 

 nitrogen procured in numerous experiments 

 on the blood of calves, oxen, and horses, pre- 

 viously agitated with atmospheric air, was, 

 when reduced to the temperature of 32 Fahr. 

 and the mean barometric pressure, from T7 

 to 3*3 per cent, of the volume of the blood 

 employed. The quantity of oxygen gas which 

 blood is capable of absorbing from the atmo- 

 spheric air, is, according to Magnus, from 10 

 to 13 times more than water can do under 

 the same circumstances.f The experiments 



* PoggendorfPs Annalen, Band Ixvi. S. 189. Gay 

 Lussac (Annales de Chimie et de Physique, 3me 

 serie, torn. x. p. 1. 1844), has brought forward va- 

 rious objections against the inferences drawn by 

 Magnus from his experiments. He asserts that 

 they lead to the conclusion that more carbonic acid 

 gas exists in arterial than in venous blood. Mag- 

 nus has replied, and on the whole successfully, to 

 these objections of Gay Lussac (Opus cit. Band Ixvi). 

 He contends that as the quantity of gases procured 

 was only a part of what the blood actually contained, 

 and as the experiments were of different duration, it 

 must lead to error to compare, as Gay Lussac has 

 done, the relative quantities of carbonic acid gas 

 obtained from corresponding quantities of the two 

 kinds of blood; and that the legitimate mode of 

 procedure under the circumstances of the case, is to 

 compare, as has been done in the above table, the 

 relative quantities of the whole of the gases procured 

 from each of the two kinds of blood. 



f Poggendorff 's Annalen, Band Ixvi. S. 202. In 

 some experiments the quantity of nitrogen absorbed 

 by the blood, when previously agitated with carbonic 

 acid, was 6-5 per cent. Though these various results 

 obtained by Magnus in his experiments have not 

 been fully confirmed by others, indeed several expe- 

 rimenters, such as Enschut, Bischoff, and Dr. J. 

 Davy, who succeeded in procuring carbonic acid gas 

 both from venous and arterial blood, failed in ob- 

 taining decided evidence of the presence of oxygen 

 gas, yet they appear to have been so carefully and 

 repeatedly performed, that a belief in their general 



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