864 RESPIRATION AND OXIDATION. 



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 1 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, STRASSBURG, 

 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 



iCentralbl. f. Physiol. 23, 274; Skand. Arch. f. Physiol., 22, 221 (1909). 

 2 Skand. Arch. f. Physiol., 25, 169 (1911); Proc. Roy. Soc., 1911; see also Journ. 

 of Physiol., 44, 305 (1912). 



3 Skand. Arch. f. Physiol., 20, 263; 23, 179, 200, 213, (1910). 



4 Arch, intern, de Physiol., 10, 391 (1911). 



5 Wolffberg, Pfliiger's Arch., 6; Strassburg, ibid.', Nussbaum, ibid., 7. 



