12 HEMOGLOBIN 



Both these questions can be answered in the affirmative. Hill and 

 Holden(5), working in the Cambridge Biochemical Laboratory, have 

 succeeded in preparing haemoglobins corresponding to hsemato- 

 porphyrin and mesoporphyrin — a process which involves not merely 

 the production of the oxyhaemoglobin itself but on the way the 

 corresponding haemin, methsemoglobin and reduced haemoglobin. 

 Thus there is no reason why nature should not abound with countless 

 forms of haemoglobin each differing from its neighbour by some 

 trifling dissimilarity in the structure of its specific porphyrin. Hitherto 

 only one form of haemoglobin has been found in nature which has a 

 porphyrin basis other than that of protoporphyrin. That haemoglobin 

 occurs very far down in the animal kingdom (in some polychaete 

 worms) and for a reason which we do not know nature seems not to 

 have persisted in it. It is called chlorocruorin. 



Chlorocruorin is, if I may say so, an old love of Ray Lankester's(6); 

 he first described it and, as I know by talking with him, he has never 

 lost interest in it and in the discovery of its relation to haemoglobin. 

 Green in dilute solution, chlorocruorin is reddish when more con- 

 centrated. Lankester showed that it could be oxidised and reduced 

 as haemoglobin could be, and that like haemoglobin the oxy-body 

 had two absorption bands in the visible spectrum whilst the reduced 

 body had but one. The bands of chlorocruorin, whilst similar to those 

 of haemoglobin, are not identical with the haemoglobin bands in 

 position. They are nearer the red end of the spectrum, not by a 

 little but by a great deal. The j3-band of chlorocruorin (that nearest 

 the blue end of the spectrum) occupies a position about haK-way 

 between the a- and j3-bands of haemoglobin, whilst the a-band of 

 chlorocruorin is displaced correspondingly towards the red. The actual 

 difference in the positions of maximum density of the a-bands of 

 chlorocruorin and of haemoglobin is of the order of 250-300 

 Angstrom units. So great a difference is not surprising in the light 

 of the work of Hill and Holden, for the haemoglobins (and their 

 derivatives) prepared from meso- and from haematoporphyrins 

 had spectra of the same general character as those of the corre- 

 sponding compounds of ordinary haemoglobin, but considerably dis- 

 placed towards the blue end. The spectrum of haemoglobin therefore 

 occupies a position intermediate between that of chlorocruorin and 

 those of the haemoglobins made from meso- and haematoporphyrins. It 

 is to H. Munro Fox (7) that we owe our recent knowledge of chloro- 

 cruorin. He it was who solved the problem so near to Lankester's 



