294 



RESPIRATION 



TABLE SHOWING THE DISSOCIATION OF OXHEMOGLOBIN IN THE PRESENCE OF VARY- 

 ING TENSIONS OF CARBON DIOXIDE. (BANCROFT AND CAMIS.) 



The salts of the blood alsb influence the oxygen fixation by hemoglobin 

 under a given tension as indicated in the following table: 



TABLE SHOWING THE INFLUENCE OF THE PRESENCE OF DIFFERENT SALTS ON 



THE PERCENTAGE OF SATURATION OF HEMOGLOBIN UNDER A 



CONSTANT OXYGEN TENSION OF 30 MM. MERCURY. 



(BANCROFT AND CAMIS.) 



1. Hemoglobin in water dissociation 60 per cent. 



2. Hemoglobin in o . 7 per cent. NaCl dissociation. ... 75 per cent. 



3. Hemoglobin in Ringer's solution dissociation 85 per cent. 



4. Hemoglobin in NaHCO 3 solution dissociation 89 per cent. 



5. Hemoglobin in 0.9 per cent. KC1 dissociation 91 per cent. 



6. Hemoglobin in Na 2 HPO 4 solution dissociation. ... 93 per cent. 



Bancroft and Camis find that the dissociation curve also varies in the 

 blood of different animals. Strassburg gives the oxygen tension of arterial 

 blood as 29.64 mm. of mercury, and for venous blood 22.04 mm - of mer- 

 cury. That is to say, during the brief interval in which the blood is in 

 the pulmonary capillaries the oxygen tension has increased by 7 . 6 mm. 

 of mercury, an increase of tension which would produce very little increase 

 in simple absorption of oxygen. Yet it is sufficient to cause fixation of 

 from four to five volumes per cent, of oxygen by the hemoglobin. 



It is evident that there will be diffusion of oxygen from the high tension 

 toward the lower and in the direction indicated by the arrows in the table 

 above. As fast as the oxygen diffuses into the venous blood, thus tending to 

 raise the pressure of the gas in solution, it is taken up and fixed by the hemo- 

 globin. This process proceeds during the interval the blood is in the pul- 

 monary capillaries far enough to raise the oxygen tension from 22.04 mm - 

 of mercury to 29 . 64 mm. of mercury, and also far enough to permit of the 

 fixation of from four to five volumes per cent, of oxygen. The oxygen 

 diffusion pressures are indicated as follows: 



