Chapter V 



defined be true the oxygen pressures on the two curves (0 CO 2 and 

 40 mm. C0 2 ) for any given percentage saturation should be in the 

 ratio of 10 to 24. In other words the effect of the CO 2 is to make 

 24 mm. oxygen pressure behave like 10 mm., and x mm. pressure 

 behave like x x . 



Here we find ourselves facing the question of whether the effect 

 of " reaction " is of a fundamentally different character from that of 

 salts. The effect of salts was to produce a curve essentially different 

 from that which would be obtained in their absence. The dissociation 

 curve of pure haemoglobin is a hyperbola, that of haemoglobin in 



100 



90 

 80 

 70 

 60 

 50 

 40 

 30 

 20 

 10 



10 20 30 40 50 60 70 80 90 100 



FIG. 30. Ordinate = percentage saturation with oxygen. Abscissa = oxygen pressure in 

 mm. The abscissa corresponding to any percentage saturation on Curve I is 11/20, 

 on Curve II 16/20, and on Curve III 27/20, of the abscissa corresponding to the same 

 percentage saturation on the dissociation curve of my blood at 40 mm. CO 2 pressure. 

 Determinations: 3mm. O 20 mm. 90mm. CO 2 pressure. 



salt solution is something else, namely an S-shaped curve. But if 

 I have correctly described the effect of " reaction," it does not affect 

 the essential character of the curve, but merely the scale on which 

 it is drawn. This conception is fundamentally different from that 

 with which I finished Chapter IV. There was no other suggestion 

 in it than that the effects of acids and salts might turn out to be 

 the same. 



The question is one which must be put to the test of experiment. 

 The effect of acid, as I have described it, was suggested to Douglas 



