862 RESPIRATION AND OXIDATION. 



KROGH l 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 hemoglobin 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 Hiifner, Arch. f. (Anat. u.) Physiol., 1890; Fr6dericq, Centralbl. f. Physiol., 7, 

 and Traveaux du laboratorie de 1'institute de physiologie de Liege, 5, 1896. 

 8 Haldane, Journ. of Physiol., 18; Haldane and Smith, ibid., 20. 

 * Skand. Arch. f. Physiol., 23, 217, 253. 



