THE SPECIFICITY OF HEMOGLOBIN 



43 



At present we know but little of any classification of the positions 

 of the spectral bands. In so far as there is any phylogenetic arrange- 

 ment the only things that. can be said at present with regard to the 

 a-band of oxyhsemoglobin are : (1) The band is nearest the red in two 

 flies — or rather their larvae, Gastrophilus and Chironomus, 5782 a.tj. 

 (2) It is nearest the blue in the worms, Liunibricus and Arenicola (8), and 

 is similarly situated in the mollusc (5760-5745 a.tj.). (3) It occupies an 

 intermediate position in the vertebrates (5773-5760 a.tj.). What these 

 differences mean when translated into terms of function, or whether 

 they have any meaning, is not known. But though the cause of the 

 difference in span in different animals is unknown, it is likely enough 

 to be important. My reason for saying so is the following: 



Already it has been stated that different animals of the same species 

 may have different spans. Within my small experience, that is par- 

 ticularly true of rabbits. When discussing the matter once with 

 Sir Charles Sherrington, he made the suggestion that the span in 

 rabbits differed, not because of any hereditary disparity, but because 

 some rabbits were not in such good health as others. The suggestion 

 would be no less than that the span of a rabbit's blood can change. 

 And this appears to be the case. Litarczek and Stromberger(9), 

 working in the Cambridge laboratory on anaemia, put the matter to 

 the test. They determined the span by the Hartridge reversion spectro- 

 scope in the case of six rabbits, while W. H. Forbes determined it 

 for them photographically in the case of one. 



The following are the data of the rabbit on whose blood Forbes 

 made the photographic observations ; they are compared with those 

 of my own blood, which may serve as a standard since the measure- 

 ments are in arbitrary units : 



(Ditto) after 

 Barcroft blood Normal rabbit treatment 



Span in arbitrary units 3-77 3-25 2-62 



(59 A.TJ.) 



The rabbits were subject to a certain experimental procedure, the 

 iijifluence of which is obscure, the one important fact being that the 



