RESPIRATION 



73 



with great accuracy the percentage saturation of haemoglobin 

 with CO. 



With the help of this method Douglas and I worked out "dis- 

 sociation curves for the CO-haemoglobin of human blood at 

 38 C in the absence, of course, of oxygen, but in the presence 

 of varying partial pressure of CO 2 - 25 The results are shown in 

 Figure 21. 



too 



90 

 80 

 70 



50 

 40 

 30 



10 



4 



c* 



o 0</ 



O05 -010 -015 -O20 -025 -0*30 -035 '040 -O45 -0>5O 



PRESSURE OF CO IN PERCENTAGE OF ONE ATMOSPHERE. 



Figure 21. 



Dissociation curves of CO haemoglobin in absence of oxygen, at 38 and 

 with various pressures of CO 2 . O Blood of C. G. D. Blood of J. S. H. 



These curves, like the curve for the oxyhaemoglobin of human 

 blood in Figure 20 are drawn free-hand. On comparing them we 

 found that, allowing for possible small errors due to insufficient 

 determinations, they are all the same curve when the scale on 

 which the abscissae of each are plotted is altered by a suitable 



26 Douglas, J. S. Haldane, and J. B. S. Haldane, Sourn. of Physiol., XLIV, p. 

 275, 1912. 



