590 THE GASES OF THE BLOOD 



therefore, the oxygen supply to the tissue is favored by 

 increased dissociation of the oxyhaemoglobin. 24 According 

 to Hasselbach 25 a transitory lowering of the oxygen fixing 

 power of the blood can be produced by lowering of the 

 atmospheric pressure. 



Influence of the Salts in the Medium, and Other Factors. 

 The saline constituents of the medium are also un- 

 doubtedly of much physiological importance. If a ten 

 per cent, haemoglobin solution in one per cent, soda solu- 

 tion be prepared the oxygen fixation is apparently firmer 

 than in blood under comparable conditions. 26 Barcroft and 

 his colleagues 27 have concluded that the course of the pres- 

 sure curve is so highly dependent upon the nature and con- 

 centration of the salts of the surrounding medium, that we 

 can scarcely contemplate the formulation of a generally 

 applicable dissociation curve. If an examination be made, 

 for example, of one and the same haemoglobin dissolved in 

 distilled water, in 0.7 per cent, salt solution, and 0.9 per 

 cent, calcium chloride solution, and in the presence of sodium 

 bicarbonate or sodium monophosphate, altogether different 

 pressure curves result. By adding the salts which belong 

 in the corresponding blood corpuscles to a solution of dog 

 (or human) haemoglobin the characteristic curve for the 

 particular blood will be obtained. 



Physical-chemical Conception of Oxygen Fixation by 

 Hemoglobin. The entrance of lactic acid into the blood may 

 also distinctly modify the course of the curve of oxygen 

 pressure. According to Barcroft more favorable conditions 

 for the supply of oxygen to the tissues are likely to obtain 

 at great heights because of diminution of the blood 

 alkalescence. 



24 Cf. A. Durig, Handworterb. d. Naturwissensch., Jena, G. Fischer, 1, 692. 



25 K. A. Hasselbach, Festschr. 0. Hammersten, Wiesbaden, 1906; cited in 

 Jahresber. f. Tierchemie, 36, 166, 1906. 



28 Cf. A. Lowy, Handb. d. Biochem., 4', 52, 1908. 



27 J. Barcroft, with Camis and Roberts, Jour, of Physiol., 39, 118, 143, 

 1909. 



