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OXYGEN TENSION IN BLOOD. 861
globin in the arterial blood that the tension of the oxygen in the arterial
blood must be relatively higher. This is substantiated by the earlier
observations of Bert and Hufner, as well as by the determination.-,
of Herter, Fredericq and others, 1
using aerotonometric methods,
which will be mentioned below in connection with the carbon dioxide
tension. Herter found the oxygen tension in the arterial blood of
dogs to be equal, on an average, to a pressure of 78.7 mm. Hg and Fre-
dericq, by a better method, found that it was equal to 91-99 mm. Hg.
The oxygen tension of the venous blood of dogs has been found by
aerotonometric means to be equal to 20.6-27.7 mm. (Strassburg,
Falloise), and by means of the lung-catheter (see below) equal to 25.5-27
mm. (Wolfberg, Nussbaum). For human venous blood Loewy and v.
Schrotter 2
found an average of 37.68 mm. Concerning the question
as to the mechanism of taking up oxygen in the lungs these figures are of
less interest than the oxygen tension in the arterial blood, that is, that
which has left the lungs, whose tension is estimated as 90 to about 100
mm. Hg as given above.
These results do not coincide with the investigations of Bohr,3
who
in many cases obtained essentially higher figures for the oxygen tension
in arterial blood.
He experimented on dogs, allowing the blood, whose coagulation had been
prevented by the injection of peptone solution or infusion of the leech, to flow
from one bisected carotid to the other, or from the femoral artery to the femoral
vein, through an apparatus called by him an haemat aerometer. The apparatus,
which is a modification of Ludwig’s rheometer (stromuhr), allowed, according
to Bohr, of a complete interchange between the gases of the blood circulating
through the apparatus and a quantitjr
of gas whose composition was known at
the beginning of the experiment and inclosed in the apparatus. The mixture
of gases was analyzed after an equalization of the gases by diffusion. In this
way the tension of the oxygen and carbon dioxide in the circulating arterial blood
was determined. During the experiment the composition of the inspired and
expired air was also determined, the number of inspirations noted, and the extern
of respiratory exchange of gas measured. To be able to make a comparison
between the gas tension in the blood and in an expired air whose composition was
closer to the unknown composition of the alveolar air than the ordinary expired
air, the composition of the expired air at the moment it passed the bifurcation of
the trachea was ascertained by special calculation. The tension of the gases ;
;
this " bifurcated air " could be compared with the tension of the gases of the blood
and in such a way that the comparison took place simultaneously. Recentlv
1
Pert, La pression barometrique, Paris, 1878; Herter, Zeitschr. f. phvsiol. Chem.
3; Hufner, 1. c; Fredericq, Centralbl. f. Physiol., 7, and Travaux der laborat. de
l’inst. de phvsiol. de Liege, 5, 1896.
- StrasBburg, Pfluger’s Arch., 6; Falloisi:, Bull. Acad. Roy. Belg., 1902. Wolfberg,
Pfliiger’s Arch., 4 and 6; Xussbauni, ibid., 1; Loewy and v. Schrotter, cited by Loewy
in Gppenheimer’a Elandb., 4, 76.
* Skand. Arch. f. Physiol., 2, and Nagel’s Handbuch der Physiologic
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