HEMOGLOBIN, CARBON MONOXIDE AND OXYGEN 171 



had been exposed to the existing pressure either of oxygen or CO 

 in the absence of the other. Thus 20 mm. pressure of oxygen alone 

 would have produced 68 and not 53 per cent, of oxyhsemoglobin 

 while CO, to the extent of 10 virtual mm. of oxygen, would have 

 produced 55 and not 27 per cent, of HbCO. Similarly at the point 

 lower down the curve 5 mm. of oxygen alone would have produced 



100 



90 



60 80 



70 





o 60 



50 

 40 



a 

 § 20 



10 



2 4 6 8 10 



20 

 Pressure mm. 



Fig. 54. 



30 



40 



38 and not 31 per cent, of oxyhsemoglobin, and CO to the extent of 3-1 

 virtual mm. of Og would have produced about 27 per cent, of HbCO and 

 not 9-8 per cent. That seems all straightforward and as it should be. 



I must now break it to the reader that I was guilty of some degree 

 of subtlety in selecting the hyperbolic dissociation curve as the basis 

 of my calculations, for had I chosen the dissociation curve of blood 

 we should have been faced at the outset with certain anomahes which 

 I will now proceed to describe : they are of considerable interest. 



Consider the last of the two examples given, 20 mm. Og and CO 

 equivalent to 10 mm. of oxygen. Applying these figures to the 

 ordinary dissociation curve of blood (at 40 mm. COg-pressure and 



