76 



RESPIRATION 



It is thus evident that when we have determined the percentage 

 saturations of a sample of haemoglobin with CO and O2 in a solu- 

 tion saturated with a gas mixture containing CO and O2 at known 

 concentrations or partial pressures, what we have really de- 

 termined is the relative affinities of the haemoglobin for CO and 



100 



90 - 



70 



CO 



o 



2 

 560 



ii.«50 

 o 



z 

 o 



K40 



«o 



^ 



20 



a 10 



10 



20 



v30 40 >50 60 70 



PERCENTAGE OF OXYGEN. 



80 



90 



• 00 



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. 



O2 (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 Og when the partial pressures 

 of CO and O2 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 O2. 

 For the haemoglobin of Douglas the corresponding figure is 246. 

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



