360 



RESPIRATION. 



of Dr. J. Davy, Mitscherlich, Ginelin and 

 Tieilemann, Enschut and Magnus, prove 

 that venous blood can absorb considerably 

 more than its own volume of carbonic acid 

 gas ; and according to Mitscherlich, Gmelin 

 and Tiedemann, and Enschut, more of this 

 gas can be absorbed by arterial than by venous 

 blood.* 



Lehmann has endeavoured to ascertain the 

 relative quantities of free and combined car- 

 bonic acid in the blood. In twelve experi- 

 ments upon bullock's blood the average quan- 

 tity of free carbonic acid in 1000 grammes 

 (154.33-0 Troy grains) of blood, was 0'132 

 gram. ( 1-937 grains) of free, and 0'6759 gram. 

 (]0'431 grains) of combined carbonic acid: 

 or, estimating these quantities by volume, in 

 61"250 English cubic inches of blood, there 

 were 4'271 cubic inches of free, and 2T9G8 

 cubic inches of combined carbonic acid.f 



The results obtained on causing animals to 

 breathe gases devoid of oxygen are in unison 

 with those derived from direct experiment, and 

 furnish additional evidence in proof of the 

 existence of free gases in the blood. That a 

 quantity of carbonic acid gas may be exhaled 

 from the blood during the respiration of gases 

 devoid of oxygen is proved by the experiments 



accuracy is justly almost universally entertained by 

 physiologists. Marchand (Journal flir praktische 

 Chemie, Band xxxv. S. 391) is the on\y other che- 

 mist, as far as we are aware, who has procured 

 oxygen gas from the blood. He ascertained, by 

 qualitative but not by quantative analysis, that 

 oxygen gas is contained in the venous blood of the 

 dog. 



It has been argued, and the objection is antici- 

 pated and examined by Magnus, that part of the 

 carbonic acid gas obtained from the blood in the 

 above experiments may not have existed in the free, 

 but in the combined state in the blood. It has been 

 proved by the experiments of Heinrich Rose (Pog- 



fendorff's Annalen, Band xxxiv. S. 149. 1835), and 

 larchand (Journal fiir praktische Chemie, Band 

 xxxv. S. 389, 390. 1845), that when a solution of 

 bicarbonate of soda is agitated with, or even exposed 

 for some time to, atmospheric air or hydrogen, it gives 

 off part of its carbonic acid, and becomes a sesqui- 

 carbonate ; and if heat be now applied, an additional 

 quantity of carbonic acid is given off, and it is re- 

 duced to the state of carbonate of soda. If, there- 

 fore, bicarbonate of soda exists in the blood, part of 

 the carbonic acid gas obtained in the experiments 

 of Magnus and others may have been derived from 

 this source. The exact condition of the carbonates 

 of soda in the blood is not known : indeed their ex- 

 istence there has lately been called in question by 

 Enderlin (Annalen der Chemie und Pharmacie, 

 Band xlix. S. 317) and Liebig (idem opus, Band 

 Ivii. S. 120. 1846), but without sufficient reason, as 

 Marchand (Journal fiir praktische Chemie, Band 

 xxxvii. S. 321. 1846), Lehmann (idem opus, Band 

 xl.), and Moleschott (Hollandische Beitrage, Band i. 

 hedft ii. S. 1(53. 1847) have shown.' 



* Dr. J. Davy (Philos. Transact, for 1838, p. 298) 

 has made an important observation on the absorbing 

 capacity of the blood, for carbonic acid under different 

 circumstances. In two animals, one of which was 

 killed by strangulation, the other by exhaustion of 

 the air of the lungs by the air-pump, the blood of 

 the former absorbed only 150 per cent., that of the 

 latter 370 per cent, 



t Journal fiir praktische Chemie, von Erdmann 

 und Marchand, Band xl. S. 133. 1847. 



of Spallanzani* and Dr. W. F. Edwards f on 

 the products of the respiration of snails con- 

 fined in hydrogen and azote ; those of Dr. W. 

 F. Edwards J on a fish (Cyprinus aureus) 

 confined in water saturated with hydrogen; 

 those of Dr. W. F. Edwards , Collard de Mar- 

 tigny||, Miiller and Bergemann f , Bischoff** 

 and Marchand f f, on frogs confined in hy- 

 drogen or azote ; and those of Dr. W. F. 

 Edwards JJ, upon the young of certain of 

 the mammalia confined in hydrogen gas. The 

 experiments of Nysten $$, in which he first 

 exhausted the air, as far as possible, in the 

 lungs of adult dogs, and then caused them to 

 breathe hydrogen or azote; and those of Sir 

 H. Davy [| || , and of Coutanceau and Nysten IfH, 

 on the respiration of nitrous oxide and azote 

 in their own persons, though not free from 

 serious objections, are still, as far as they go, 

 in favour of the opinion that free carbonic 

 acid gas is contained in the blood. 



In a former part of this article we have de- 

 tailed several observations, both upon the 

 human species and the lower animals, to prove 

 that a quantity of azote is frequently exhaled 

 in respiration. The experiments of Allen and 

 Pepys***, and Nysten ftt> show that the 

 exhalation of azote is considerably increased 

 by breathing oxygen or hydrogen, or a mixture 

 of these two gases, and thus afford additional 

 evidence that free azote exists in the blood. 

 Marchand concludes from his experiments on 

 frogs, that when they are made to breathe 

 pure oxygen gas, azote is evolved from the 

 blood, and that when made to breathe pure 

 hydrogen, both oxygen and azote are evolved 

 from the blood. Jjj 



Differences in the form of the red corpuscles 

 in venous and arterial blood. The physical 



* Me'moires sur la Respiration, p. 346 to 351. 



f De 1' Influence des Agens Physique sur la Vie, 

 p. 449. 1824. 



J Opus cit, p. 447, 448. 



Opus cit. p. 442 to 447. 



|| Magendie's Journal de Physiologic, torn. x. 

 p. 122 to 124. 



^f Muller's Elements of Physiology, translated 

 by Baly, vol. i. p. 354. 



** Commentatio de Novis quibusdam Experi- 

 inentis Chemico-Physiologieis, p. 20. 



ft Journal fiir praktische Chemie, Band xxxiii. 

 S. 154. 1844. Marchand thinks that in the experi- 

 ments of those who preceded him, upon the respira- 

 tion of frogs in hydrogen, that the gas employed 

 must have contained some oxygen, as the animals 

 lived longer than those used in his experiments 

 where the gas was quite pure. 



II Opus cit. p. 453 to 455. 



Recherches de Physiologic et de Chimie Patho- 

 logiques, p. 225 to 229. 



|| || Researches, Chemical and Philosophical. Divi- 

 sion II. 



^f*|f Coutanceau's ReVision desNouvelles Doctrines 

 Chimico-Physiologiques, p. 280 to 302. 1821. Cou- 

 tanceau and Nysten breathed azote alone ; and their 

 experiments were regarded, even by Coutanceau 

 himself, as " essais bien incomplete." Opus cit. p. 

 301, 302. 



*** Philos. Trans. 1809, p. 404. 



tft Recherches, &c. p. 230, 231. 



III Opus cit. Band xxxiii. S.154 159. Band xxxv. 

 S. 386 389. Marchand does not distinctly state 

 that he ascertained this by direct analysis of the 

 expired gases. 



