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862 RESPIRATION AND OXIDATION.
Krogh • constructed an apparatus, called by him microtonometer, to be used
for the same purpose.
Bohr found remarkably high results for the oxygen tension in arterial
blood in this series of experiments. They varied between 101 and 144
mm. Hg pressure. In eight out of nine experiments on the breathing
of atmospheric air, and in four out of five experiments on breathing air
containing carbon dioxide, the oxygen tension in the arterial blood was
higher than the " bifurcated air." The greatest difference, where the
oxygen tension was higher in the blood than in the air of the lungs, was
38 mm. Hg.
Hufner and Fredericq 2
have made the objection to Bohr’s experi-
ments and views that a perfect equilibrium had probably not been
attained between the air in the apparatus and the gases of the blood.
Fredericq, by new experiments, presents strong objections to the
acceptance of Bohr’s findings, while on the other hand Bohr not only
defends his experiments, but also finds errors in the experiments of his
opponents, while Haldane and Smith’s 3
experiments, making use of
an entirely different principle, tend to corroborate the high results attained
by Bohr.
Haldane’s method is as follows : The individual experimented upon is allowed
to inspire air containing an exactly known but small quantity of carbon monoxide
(0.045-0.06 per cent), until no further absorption of carbon monoxide takes place
and the percentage saturation of the haemoglobin in the arterial blood with carbon
monoxide has become constant, as shown by a special titration method. This
percentage saturation is dependent upon the relation between the tension of the
oxygen in the blood and the tension of the carbon monoxide, as known from the
composition of the inspired air. When this last and the percentage saturation
with carbon monoxide and oxygen are known the oxygen tension in the blood
can be easily calculated.
According to this method Haldane and Smith found still higher
figures than Bohr for the oxygen tension in the blood, and they calculated
the average tension of the oxygen in human arterial blood to be equal
to 293 mm. Hg.
Based upon the experiments of A. and M. Krogh, which will be dis-
cussed below (page 864) A. Krogh 4
has presented objections to the
experiments of Haldane and Smith.
Let us now compare the figures for the oxygen tension of the arterial
blood as found by various investigators with the tension of the oxygen
in the air of the lungs.
1
Skand. Arch. f. Physiol., 20.
2
Hufner, Arch. f. (Anat. u.) Physiol., 1890; Fredericq, Centralbl. f. Physiol., 7,
and Traveaux du laboratorie de l’institute de physiologie de Liege, 5, 1896.
3
Haldane, Journ. of Physiol., 18; Haldane and Smith, ibid., 20.
Skand. Arch. f. Physiol., 23, 217, 253.
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