172 



HEMOGLOBIN 



37° C), the reduced haemoglobin amounts to 48 per cent., the 

 oxy- + carboxy- to 52 per cent., and as before two-thirds of this will 

 be oxy haemoglobin and one-third carboxyhsemoglobin, so that the 

 final composition of the mixture would be (Fig. 55) : 



Reduced haemoglobin 48 per cent. 

 Oxy haemoglobin 35 ,, 



Carboxyhaemoglobin 17 ,, 



Total haemoglobin 100 ,, 



Here is the apparent anomaly. Twenty mm. of oxygen pressure in 

 the absence of CO would only produce 27 per cent, of oxyhaemoglobin, 



§ 60 



50 



40 



30 



20 



PLi 



10 



10 



20 

 Pressure mm. 

 Fig, 55. 



30 



not 35 per cent. CO equivalent to 10 mm. of oxygen would only 

 produce 6 per cent, of HbCO, not 17 per cent. Therefore the mixture 

 of oxyhaemoglobin and carboxyhaemoglobin is richer in either of the 

 two, if the CO and O2 are presented simultaneously, than would be 

 the case if O2 or CO were in equiUbrium with haemoglobin in the 

 absence of the other. 



A few examples will show the reader, if it is not already apparent 

 to him, that this paradox is essentially due to the concavity (viewed 

 from the ordinate) of the lower part of the dissociation curve. Such 

 a paradox might well shake one's faith in the whole method of treat- 

 ment adopted, namely, that of regarding the reactions of haemoglobin 



