7 6 2 CHEMISTR Y OF RESPIRA TION. 
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 Pert, 3 
Hirschmann, 4 and Pfluger 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.''' 
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 gases 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 Pfluger, 8 and others. 9 The 
most important discovery in this connection is that made by Pfluger ; 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 lie 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 dog'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. cle Vanat. etphysiol. etc., Paris, 1865, tome ii. p. 302. 
;i "Lecons sur la physiol. conip. de la respiration," Paris, 1870, p. 118. 
4 Arch. f. Anut., Physiol, u. tvissensch. Med., 1866, S. 502. 
8 Arch. f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 274. 
6 Mathieu and Urbain, Arch, dephysiol. norm, etpath., Paris, 1871, tome iv. ; Pfliiger, 
Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 75. 
7 Wicn. med. Jahrb., 1865, Bd. xxi. S. 145. 
8 Arch.f. d. ges. Physiol., Bonn, 1868, Bd. i. S. 61. 
9 Hammarsten, Ber. d. k. siichs. Gcsellsch. d. Wisscnscli. Math.-phys. CI, 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. 
n Setschenow, Sitzungsb. d. h. Alcad. 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. 
ia "La pression barometrique, " Paris, 1878, p. 1038. 
