CHAPTER II 



PORPHYRINS 



X HEEE are stories in Cambridge which go back to the days in which 

 Michael Poster sowed such seed as grew up to form the Enghsh 

 school of modern physiology. One of these stories has to do with 

 his pupil, Francis Maitland Balfour, the embryologist. It is related 

 (with what truth I cannot say) that Balfour as a young man asked 

 Foster to suggest to him a subject for research. Foster was taking 

 lunch at the time and before him was a boiled egg. He pointed to 

 the egg and said, "What better subject can you have than that?" 

 And there the study of haemoglobin may commence also; for the 

 particular material which at the moment is regarded as the material 

 starting-point in hsemoglobinology is porphyrin, the brown colouring 

 matter of many eggs. I say "at the moment" because twenty years 

 ago, or even less, the study of haemoglobin was supposed to have its 

 source in chlorophyll; but the most competent judges, for instance 

 Willstatter(i), regard it as difficult to attach evolutional significance 

 to the chemical similarity between chlorophyll and porphyrin. Even 

 though the view that haemoglobin in the animal kingdom is the direct 

 result of chlorophyll which is eaten in vegetable food has found recent 

 supporters in Verne (2) and Marchelewski(3), it seems not proven. Let us 

 commence then with porphyrin as being the simplest pigment which 

 has evident chemical relationships with haemoglobin. 



Porphyrin, apart from its existence in the egg-shell, does not bulk 

 very large in warm-blooded animals, though in small quantities it 

 is widely distributed. In the earthworm it constitutes the line of 

 pigment down the back and is found in many other places in inverte- 

 brates (MacMunn, Dhere, Derrien). To distinguish it from the other 

 members of its class (which comprises other natural porphyrins such 

 as uro- and coproporphyrin) it is known as Kammerer's porphyrin. 

 More recently it has been called by Hans Fischer (4) (who has crowned 

 a compendious series of researches by synthesising some members 

 of the porphyrin group) protoporphyrin. The names ooporphyrin 

 and Kammerer's porphjrrin are significant, for they serve to remind 

 the reader that the material found in the egg-shell is the same as 

 that obtained from blood by Kammerer. He produced this substance 

 as a degradation product of haemoglobin by the action on it of 



