358 



RESPIRATION. 



blood, mentioned above. Michaelis *, and 

 Marcet and Macairef, in their ultimate or 

 elementary analyses of both kinds of blood, 

 found more carbon and less oxygen in ve- 

 nous, and less carbon and more oxvgen in 

 arterial blood ; but Berzelius has adduced 

 sufficient reasons to induce us to doubt whe- 

 ther, in such investigations, at least as at 

 present conducted, the distinctive characters 

 of the two kinds of blood can be preserved 

 during the analysis, and that they are de- 

 serving of any confidence. J 



A larger quantity of fixed carbonic acid 

 has been obtained from venous than from 

 arterial blood by Mitscherlich, Gmelin, and 

 Tiedemanu.$ 



It is now placed beyond dispute that 

 free gases exist in the blood, and it be- 

 comes a point of great importance in de- 

 ciding upon the true theory of respiration 

 to ascertain their nature, quantity, and rela- 

 tive proportions in the two kinds of blood. 

 Four methods have been followed in pro- 

 curing the free gases from the blood. 1. By 

 the application of heat. 2. By the use of 

 the air-pump. 3. By agitation of the blood 

 with other gases. 4. By the respiration of 

 other gases than atmospheric air. 



The first of these methods is imperfect, as 

 the albumen coagulates when the temperature 

 is raised towards the boiling point, and may 

 retain gases present in the blood. The se- 

 cond method is also liable to lead to negative 

 results, unless the air-pump employed be of 

 the best construction, for, according to Mag- 

 nus, it is not until the pressure of the air 

 within the bell-glass is reduced to one inch, 

 that the gases begin to escape from the blood. 

 In such experiments it is also necessary to 

 employ blood from which the fibrin has been 

 removed, for coagulated blood will retain the 

 free gases, and prevent their escape. 



Sir H. Davy stated that by raising the 

 temperature gradually to 200 Fahr., he ob- 

 tained from 12 cubic inches of the arterial 

 blood of a calf l-J^ cubic inch of carbonic 

 acid gas, and -^ of a cubic inch of oxygen || ; 

 and that he procured carbonic acid gas from 

 human venous blood heated to 112 Fahr.! 

 Euschut assures us that, by subjecting blood 

 to the temperature of boiling water, he ob- 

 tained carbonic acid gas both from venous 

 and arterial blood, and a greater quantity 

 from the former than the latter kind of 



_ * Diss. Inaug. de Partibus Constitutionis singula- 

 rium Partium Saueuinis arteriosi et venosi. Berolini, 

 1827. 



t Annales de Chimie et Physique, torn. li. p. 382. 

 1832. 



J Lehrbuch cler Chemie, Band iv. S. 99, 100. 

 Dresden, 1831. 



Zeitschrift fur Physiologic, Band v. 1833. Mit- 

 scherlich, Gmelin and Tiedemami, by the addi- 

 tion of acetic acid, and the application of heat, ob- 

 tained from 1000 parts of venous blood at least 12-3 

 parts, and from the same quantity of arterial blood 

 8-3 parts of combined carbonic acid. 



|| Beddoes' Contributions to Physical and Medical 

 Knowledge, p. 132. 1799. 



! Idem opus, p. 134. 



blood.* It is alleged that Brande obtained 

 carbonic acid gas both from venous and ar- 

 terial blood in considerable quantity by the 

 use of the air-pump f; and Scudamore states 

 that he procured it by the same means in 

 variable quantities from venous blood.J Col- 

 lard de Martignyf and Enschut|| procured 

 carbonic acid gas both from venous and 

 arterial blood, by placing them in the Torri- 

 cellian vacuum, and a larger quantity from 

 the former than from the latter. Nasse, sen.!, 

 Stevens**, Dr. G. Hoffman ff, Enschut JJ, Dr. 

 Maitland , and Bischoff'H || , obtained carbonic 

 acid gas from venous blood on agitating it 

 with hydrogen, or by allowing this gas to 

 stand over the blood for several hours. The 

 existence of free carbonic acid gas in the 

 blood was still, however, regarded by some 

 physiologists as very problematical, since se- 

 veral trust-worthy and careful experimenters, 

 such as Dr. J. Davy!!, Mitscherlich, Gmelin, 



* Dissertatio Physiologico-Medica de Respira- 

 tionis Chymismo, p. 96 to 99. 1836. Enschut, in 

 one set of experiments, obtained in this manner from 

 40 cubic centimetres (2-440 English cubic inches) of 

 each kind of the blood of the calf, 2 to 4 cubic centi- 

 metres (-12205 to '24410 English cubic inches) of car- 

 bonic acid gas from venous blood, and 1 to 2'5 cubic 

 centimetres (-061025 to -15256 English cubic inches) 

 of the same gas from arterial blood, p. 99. Enschut 

 points out various precautions necessary to be ob- 

 served to secure accuracy in such experiments, a 

 want of attention to which, he believes, was the 

 cause of the failure of Dr. J. Davy, Miiller, and 

 others, in their attempts to obtain carbonic acid gas 

 from blood by heat, p. 100104. 



f Sir Everard Home, in London Philos. Trans, 

 vol. xxix. p. 172. 1818. It is stated by Sir Everard 

 (p. 181), that Mr. Brande obtained carbonic acid in 

 the proportion of 2 cubic niches for every ounce of 

 blood, a quantity so large, and obtained apparently 

 with such facility, as to raise insuperable suspicious 

 regarding the accuracy of the experiments. Sir 

 Everard Home (29th vol. Philos. Trans, p. 189) and 

 Scudamore state that they observed the escape of 

 free carbonic acid gas from the blood during its 

 coagulation, an observation not confirmed by 

 others. It appears that Vogel also obtained carbo- 

 nic acid from venous blood by means of the air- 

 pump. (Schweigger's Journal, Band xi. S. 401, as 

 quoted by Bischoff.) 



J An Essay on the Blood, p. 108. 1824. The 

 largest quantity of carbonic acid gas that Scudamore 

 procured from venous blood, was half a cubic inch of 

 gas from six ounces of blood. 



Magendie's Journal de Physiologic, torn. x. 

 p. 127. 1830. 



|| Opus cit. p. 115. 



! Meckel's Archiv, Band ii. 1816. Nasse al- 

 lowed the hydrogen to stand over blood from 24 to 

 48 hours. 



** Philos. Transact, vol. xlvi. p. 345. 1835. 



ft Medical Gazette, for 1832 1833, vol. xi. 

 p. 881. 



JJ Diss. de Respirationis Chymismo, p. 124 to 126. 

 Enschut obtained carbonic acid by this means also 

 from arterial blood, but in smaller quantities than 

 from venous blood. 



Experimental Essay on the Physiology of the 

 Blood, p. 52. Edinburgh, 1837. 



|||| Commentatio de Novis quibusdam Experi- 

 mentis Chemico-Physiologicis ad illustrandam Doc- 

 trinam de Respiratione institutis, pp. 17, 18. Hei- 

 delberg, 1837. Bischoff also proem-eel carbonic acid 

 gas from arterial blood by means of the air-pump, 

 pp. 11, 12. 



!! Philos. Trans, vol. xxxiv. p. 506. 1823. 



