CHAPTER I 



INTRODUCTORY 



OiR MICHAEL FOSTER (1) likened the growth of knowledge to the 

 ascent of a spiral stair from which the observer periodically surveys 

 the same landscape, but each time from a higher level than the last. 

 In the decade before the war great advances were made in an under- 

 standing of haemoglobin, and even then sufficient was known about 

 it to elicit, if not to justify, the statement (2) that haemoglobin "was 

 perhaps the second most interesting substance in the world" — the 

 first presumably being chlorophyll. The landscape spread out before 

 the observer then was that of haemoglobin behaving differently under 

 all sorts of circumstances. The point of view on the spiral which 

 was attained was the discovery that circumstances themselves had a 

 quite unexpectedly great effect in regulating the action of haemoglobin, 

 so that the question was seriously asked whether all haemoglobin 

 was not really the same. The answer at one time appeared almost 

 to be "yes." Those whose philosophy ran in the direction of a single 

 haemoglobin, had still to face the fact that the pigment from the 

 corpuscles of different animals crystalUsed differently (3). That, in 

 1910, seemed a small matter as compared with the divergences which 

 had been shown merely to be a matter of circumstance — solvent, 

 temperature, hydrogen-ion concentration and the like. With an 

 understanding of the necessity for the study of haemoglobin under 

 uniform conditions the whole question of the uniformity of haemo- 

 globin was ripe for reinvestigation, A few experiments made on 

 the subject by Douglas, Haldane and Haldane(4) before the war 

 pointed to the existence of essential differences in the haemoglobin 

 of different species. 



Since 1921 the whole matter has been gone into in great detail, 

 and to-day we are confronted with the same landscape, which ten 

 years previously appeared to consist merely of a few massive features : 

 from our present height it consists of endless detail. 



Both abroad (Vies (5)) and at home (6) it was shown that the haemo- 

 globin of Arenicola differed essentially from that of man, both 

 spectroscopically and in its gas-binding properties. The discovery of 

 this difference led to a systematic comparison of the haemoglobins 



