272 



VI. HEMOGLOBIN 



phenomenon which could not be explained except in terms of inter- 

 action between hemes. He made the acute clinical observation that 

 while miners succeeded in working when the hemoglobin content of 

 their blood had been reduced by disease to less than 50%, the reduc- 

 tion of the oxygen capacity of their blood to the same extent by 

 carbon monoxide often produced collapse. Haldane, Douglas, and 

 Haldane {1102) reinvestigated the system oxygen-carbon monoxide- 

 hemoglobin and were able to explain the phenomenon in an empirical 

 fashion on the basis of the sigmoid shape of the dissociation curve. 

 Their results were confirmed by Stadie and Martin in 1925 (2606) 

 and by Roughton and Darling (2366) in 1944. Interest in the 

 problem has recently been revived (c/., for example, Ji.38 ,17 Jf-Ji) and 

 observations have been extended to the analogous case in which 

 large amounts of hemrglobin are present (532). 



The phenomenon may be simply explained on the basis of the 

 sigmoid dissociation curve, assuming this to be of the same shape for 

 both oxyhemoglobin and carboxyhemoglobin. It has long been 

 known that when hemoglobin is completely saturated with a mixture 



q p(CO + OO 



Fig. 9. The Haldane effect. 



of oxygen and carbon monoxide, the relative amounts of the two 

 pigments can be expressed by the equation [HbC0]/[Hb02] = K X 

 VOi/Pco- Consider the sigmoid dissociation curve given in Figure 9. 

 The same degree of saturation of the pigment with oxygen will be 

 obtained at Kg units of pressure as with carbon monoxide at g units 



