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S64 RESPIRATION AND OXIDATION.
i
mm. Hg and we compare this with the highest results obtained for the
oxygen tension of the arterial blood as determined by tonometric means,
we find that the taking up of oxygen in the lungs can be simply explained
according to physical laws as a diffusion process. The conditions are
quite different if we start with the high-tension results of Bohr, 101-144
mm. Hg, or the still higher results of Haldane and Smith. The oxygen
tension in the blood is, in many cases, according to these latter authors,
always higher than the tension in the lungs, as average for various races
of animals. In these cases the passage of oxygen from the lungs to the
blood cannot be explained simply by a diffusion. We must therefore
with Bohr, accept a special activity cf the lungs, and according to,
him a secretory activity of the lungs also exists besides diffusion. In his
most recent work Bohr x
presents the view that the specific action of the
lungs essentially consists in maintaining a necessary difference in pressure
for the diffusion. Nevertheless besides this a secretory process is nec-
essary, especially for the taking up of oxygen. Based upon newer
measurements Douglas and Haldane 2
also advocate the view that the
taking up of oxygen can be brought about by diffusion alone, but that
with the existing lack of oxygen in the tissues an active secretion of
oxygen takes place in the lungs.
By means of a tonometer described by A. Krogh, he and M. Krogh
have compared the oxygen tension in the arterial blood with that in the
alveolar air. In these experiments the tension in the blood was always
found lower than in the alveolar air. From this A. Krogh 3
concludes
that the exchange of gas in the lungs is chiefly brought about by diffusion.
Fredericq 4
has recently arrived at the same view by his experiments
on the respiratory exchange of gas in aquatic animals.
As reports on the taking up of oxygen are conflicting so also are those
on the giving up of carbon dioxide.
The tension of the carbon dioxide in the blood has been determined
in different ways by Pfluger and his pupils Wolffberg, Strassbtjrg,
and Nussbaum.5
According to the aerotonometric method the blood is allowed to flow directly
from the artery or vein through a glass tube which contains a gas mixture of a
known composition. If the tension of the carbon dioxide in the blood is greater
than the gas mixture, then the blood gives up carbon dioxide, while in the reverse
case it takes up carbon dioxide from the gas mixture. The analysis of the gas
»Centralbl. f. Physiol. 23, 274; Skand. Arch. f. Physiol., 22, 221 (1909).
*Skand. Arch. f. Physiol., 25, 169 (1911); Proc. Roy. Soc, 1911; see also Journ.
of Physiol., 44, 305 (1912).
’Skand. Arch. f. Physiol., 20, 203; 23, 179, 200, 213, (1910).
fAfdh. intern, de Physiol., 10, 391 (1911).
* Wolffbonr, Pfltigef’s Arch., fi; Strassburg, ibid.; Nussbaum, ibid., 7.
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