1 86 



RESPIRATION 



evident, therefore, that the value obtained for the hydrogen ion 

 concentration is lower than that which exists in either arterial or 

 venous blood in the living body. To investigate the amount of this 

 difference Parsons 31 adopted the method of determining the hy- 

 drogen ion concentration, not in whole blood, but in its serum, of 

 which the hydrogen ion concentration is not altered when free 

 oxygen is removed. Using this method, he found that with normal 

 blood the PH at a constant pressure of CO 2 at anywhere near the 

 alveolar CO 2 pressure is greater by .038 in the oxygenated than 

 the reduced blood. Figure 55 shows his results. From them and 



8.6. 

 6-5 



8-4 

 83 

 8.2 

 81 



e-o 



79 

 78 

 77 

 76 

 75 

 74 

 73 



72 

 7/ 



\ 



\ 



MM. HG 



o 



10 



20 



30 



40 



50 



60 



70 



80 



Figure 55. 



Curve R, completely reduced blood. Curve O, fully oxygenated 

 blood. X, direct measurements on reduced blood without removal of 

 corpuscles. H, Hasselbalch's curve. 



from Figure 26 (Chapter V) it is possible to calculate what 

 the difference for normal blood between the PH of arterial and 

 mixed venous blood is, assuming that the venous blood has lost 

 a certain proportion of its oxygen and simply gained a corre- 

 sponding proportion of CO 2 . If the venous blood had lost all its 



"Parsons, Journ. of Physwl., LI, p. 440, 1917. 



