762 CHEMISTRY OF RESPIRATION. 



The results of analyses of the gases in the blood of birds and of other 

 animals are given by Zuntz. 1 



Estor and Saint-Pierre 2 concluded, from a few analyses of arterial blood, 

 that the amount of oxygen diminished in proportion to the distance of the 

 artery from the heart ; these results, however, have been shown by Paul Bert, 3 

 Hirschmann, 4 and Pfliiger 5 to be erroneous. The blood in the smaller arteries 

 contains less oxygen, but this is independent of the distance from the heart, 

 and appears to be due to the smaller number of red corpuscles, and the 

 lower specific gravity of the blood. 6 



The results given in the above table show considerable differences in the 

 percentage composition of the gases of arterial blood, even when the experi- 

 ments have been made upon similar animals. The causes of these differences 

 are partly due to variations in the gase^ in the blood, and partly to errors of 

 analysis. In order to test these points, double analyses of portions of the same 

 blood have been made by Preyer and Ludwig, 7 Pfliiger, 8 and others. 9 The 

 most important discovery in this connection is that made by Pfliiger ; 10 the 

 ordinary methods for the extraction of the gases of the blood give results 

 which for the oxygen are too low, for the carbon dioxide too high ; arterial 

 blood, when removed from the body, and kept from contact with the air, 

 rapidly becomes darker. Some of the oxygen appears to be used up by the 

 corpuscles with the production of carbon dioxide. If the blood be received 

 directly from the artery into a large vacuum, and the gases quickly extracted, 

 then values are obtained which show a higher percentage of oxygen, and a 

 lower percentage of carbon dioxide than those found by the ordinary slower 

 methods. The normal amount of oxygen in the fresh arterial blood of the 

 dog is about 22 per cent. The carbon dioxide naturally shows considerable 

 variations, but the amount of nitrogen in the most exact determinations is 

 fairly constant, about 1'8 per cent. 



The arterial blood is not quite saturated with oxygen, for by rapid 

 artificial respiration in the living animal, or by shaking arterial blood 

 with air, the amount can be raised above 23 volumes per cent. 11 Geppert 

 and Zuntz found in the arterial blood of dogs a relative saturation with 

 oxygen of 96-99 per cent. 12 The quantity of carbon dioxide in arterial 

 blood is only about one -fifth of the amount which can be held by the 

 blood, for Paul Bert 13 found that clog's blood could take up about 150 

 volumes per cent, when shaken with pure carbon dioxide. The nitrogen 

 is simply in solution and the blood appears to be saturated with that 

 gas, for the ordinary pressure and temperature. 



The gases of venous blood. On account of the differences in the 

 metabolism of the different tissues of the body, the venous blood is liable 



1 Article in Hermann's " Handbuch," Bd. iv. Th. 2, S. 41. 



2 Journ. de I'anat. et physiol. etc., Paris, 1865, tome ii. p. 302. 



3 "Lemons sur la physiol. comp. de la respiration," Paris, 1870, p. 118. 



4 Arch. f. Anat., Physiol. u. wissensch. Med., 1866, S. 502. 



5 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 274. 



6 Mathieu and Urbain, Arch, de physiol. norm, et path., Paris, 1871, tome iv. ; Pfliiger, 

 Arch. f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 75. 



7 Wien.'med. Jahrb., 1865, Bd. xxi. S. 145. 



8 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 61. 



9 Hammarsteii, Ber. d. k. sacks. Gesellsch. d. Wissensch. Math.-phys. CL, Leipzig, 

 1871, Bd. xxiii. S. 630; Afanassiew, ibid., 1872, Bd. xxiv. S. 256 ; Tschiriew, ibid., 1874, 

 Bd. xxvi. S. 120. 



10 Centralbl.f. d. med. Wissensch., Berlin, 1867, S. 321, 722. 



11 Setschenow, Sitzungsb. d. L ATcad. d. Wissensch., Wien, Bd. xxxvi. S. 289 ; Pfliiger, 

 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 70 ; Ewald, ibid., 1873, Bd. vii. S. 575. 



12 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 242. 



13 "La pression barometrique," Paris, 1878, p. 1038. 



