RESPIRATION 



79 



The explanation of the anomalous hump in the curves on Fig- 

 ures 23 and 24 is in reality easy enough in view of the peculiar 

 double-bended form of the simple dissociation curves of oxy- 

 haemoglobin and CO-haemoglobin in whole blood. When CO is 

 present at a pressure insufficient to saturate the blood, and the 



2 4- 6 8 10 12 14 16 le 20 



PRESSURE OF OXYGEN IN PERCENTAGE OF ONE ATMOSPHERE. 



22 



Figure 24. 

 Dissociation curves of CO haemoglobin in blood at 38* and in presence of 

 40 mm. CO2, with constant pressure of CO and varying pressures of oxygen. 



oxygen pressure is gradually raised from zero, the two gases to- 

 gether will trace out curves representing the total saturation of 

 the haemoglobin, as shown in the thin lines on Figure 24. These 

 curves are calculated on the theory that the proportion of oxy- 

 haemoglobin to CO-haemoglobin is exactly what is required in 

 view of the known relative affinities of oxygen and CO for the 

 haemoglobin of the blood used. As, however, the thin curves start 

 at the steep part of the joint curve a very small addition of oxygen 



