THE DISSOCIATION CURVE OF HEMOGLOBIN 99 



The experiment was performed on a solution obtained after three 

 days' dialysis in an aseptic dialyser ; this was free from the charac- 

 teristic smell which always clung to our preparation of dog's haemo- 

 globin made by Bohr's method, it was quite neutral in reaction and 

 its freedom from salts was kindly determined for us by Hardy, who 

 showed that in saline concentration it was equivalent to a '004 N 

 solution of sodium chloride. The points on the dissociation curves 

 of the two solutions were then determined, and are shown in Fig. 27. 

 The round points are those of the dialysed solution, the square ones 

 those of the undialysed solution. It was at once apparent that the 

 latter were in very close agreement with the curve published by 

 Bohr (denoted by II in the diagram), whilst the former fell so nearly 

 on the rectangular hyperbola (I) as to make it in the highest degree 

 probable that had the salts been entirely eliminated the coincidence 

 would have been complete. 



The position in 1914 was then that a dialysed solution of haemo- 

 globin of not very great concentration approximated to the hyperbolic 

 form, but did not actually reach it. That seemed a great advance, 

 but it was not reaUy satisfactory to be so near finality without 

 actually getting there. From that point the trend of events seemed 

 rather to go in the direction of showing that the mother curve from 

 which all those of the haemoglobin family were derived was not a 

 rectangular hyperbola. In collaboration with Miss Nora Tweedy (now 

 Mrs Edkins) some haemoglobin was investigated, of much greater 

 purity than that used by Roberts and myseK and also of much 

 greater concentration. The dissociation curve was definitely further 

 from the hyperbolic form than the earlier one. Adolf and Ferry (5) 

 had the same experience, as also had Adair and I (6) later. All this 

 time the "urge" had been to obtain solutions of maximum con- 

 centration. Adair (7) it was who first cut away from the tradition 

 of strong haemoglobin solutions, afiirming that haemoglobin, in its 

 most primitive condition, would be found in dilute solutions. For 

 such, however, the ordinary methods of gas analysis are useless. It 

 was tl^erefore a happy coincidence that Hartridge and Roughton(8) 

 had adapted the reversion spectroscope — which had been invented 

 to investigate the equilibrium between the four substances oxy- 

 haemoglobin, carboxyhaemoglobin, oxygen and carbon monoxide — 

 to the study of the equilibria between reduced haemoglobin, oxy- 

 haemoglobin and oxygen and also to that between reduced haemo- 

 globin, carboxyhaemoglobin and carbon monoxide. By the use of 



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