RESPIRATION 



93 



tion corresponded satisfactorily with the curves which both we 

 and he had obtained experimentally for human blood. This is 

 illustrated in Figure 27, reproduced from his paper. We had not 

 attempted to calculate the form of the curve, as several proteins 

 are involved in the chemical system; but by the simplifying as- 

 sumption which he made Parsons overcame this difficulty. 



Pco, 



10 20 30 40 50 60 7O 8O 9O IOO 110 120mm. 



Figure 27. 



Comparison between the theoretical curve and experimental results for 

 completely reduced blood of Haldane. 



In the previous chapter we have seen that, other things being 

 equal, a rise of CO 2 pressure shifts the dissociation curve of oxy- 

 haemoglobin to the right if the curve is represented as in Figure 

 19 or 28. In the living body the pressure of CO 2 is constantly 

 rising as the blood becomes more and more venous in its passage 

 through the systemic capillaries. The data embodied in Figure 25 

 gave us the means of calculating this rise, and it will be seen that 

 it is much less than previously existing knowledge would have 

 led us to believe. Figure 27 shows the oxygen dissociation curve 

 of my own blood in the living body, calculated from Figure 26, on 

 the assumption that the shifting of the curve to the right is pro- 

 portional to the increase of CO 2 pressure in the blood as it passes 

 along the systemic capillaries. 



Bohr believed that the shifting of the dissociation curve to the 

 right by the influence of increasing CO 2 pressure in the systemic 



