RESPIRATION 



75 



of blood the curve remains exactly the same when the blood is 

 diluted, or rendered less or more alkaline, or when neutral salts 

 are added. This is of course quite different from what happens 

 with the simple dissociation curves of oxyhaemoglobin and CO- 

 haemoglobin. 



15 -20 -25 



PERCENTAGE OFCO. 



Figure 22. 



Dissociation curves of CO haemoglobin in presence of air (20.9 per cent 

 O 2 ) at temperature of 38. I. Blood of J. S. H. II. Blood of C. G. D. III. 

 Blood of mouse A. IV. Blood of mouse B. The crosses indicate points deter- 

 mined in the presence of 40 mm. pressure of added COa. 



When the percentage of CO in the air is kept constant and the 

 percentage of oxygen is varied the curve is again a complete rec- 

 tangular hyperbola, as shown in Figure 23, provided that the per- 

 centage of CO is sufficient to saturate the haemoglobin completely 

 in the absence of O 2 , as in the upper curve. 



