7 6 



RESPIRATION 



It is thus evident that when we have determined the percentage 

 saturations of a sample of haemoglobin with CO and O 2 in a solu- 

 tion saturated with a gas mixture containing CO and O 2 at known 

 concentrations or partial pressures, what we have really de- 

 termined is the relative affinities of the haemoglobin for CO and 

 100 



90 



580 



60 





Q- 10 



\ 



in 



10 



20 



30 40 ,50 60 70 

 PERCENTAGE OF OXYGEN. 



80 90 



100 



Figure 23. 



Dissociation curves of CO-haemoglobin in presence of constant percentage 

 of CO and varying percentage of oxygen, at atmospheric pressure. I. Blood of 

 J. S. H. : CO = 0.0945 per cent. Blood of mouse C : CO = 0.090 per cent. 

 III. Blood of mouse D : CO = 0.0635 per cent. 



O 2 (without allowing, however, for the slight difference in solu- 

 bility between the two gases). In my own blood the haemoglobin 

 is equally divided between CO and O 2 when the partial pressures 

 of CO and O 2 are as .07 to 20.9 i.e., as I to 299. Hence the 

 affinity of the haemoglobin for CO is 299 times its affinity for O 2 . 

 For the haemoglobin of Douglas the corresponding figure is 246. 

 For his haemoglobin we can also compare the affinities for CO and 



