122 SCIENCE PROGRESS 



bination. This is not the place to enter into a detailed de- 

 scription of the many well-crystallised derivatives of chlorophyll, 

 the knowledge and spectroscopic examination of which we owe 

 chiefly to Schunck and Marchlewski. 1 



Relationship between Chlorophyll and Haemoglobin. — From our 

 point of view the most interesting derivative is the end product 

 phylloporphyrin, which is obtained from all chlorophyll deri- 

 vatives by the energetic action of alcoholic potash at 190 . It 

 crystallises well and forms blood-red solutions, showing seven 

 well-defined absorption bands. Schunck and Marchlewski had 

 previously pointed out the great similarity of the spectra of 

 phylloporphyrin and haematoporphyrin, the iron-free constituent 

 of blood pigment, and Nencki drew attention to the slight 

 difference in the molecular formulae of the two substances : 



Haematoporphyrin : Ci 6 H 18 N 2 3 

 Phylloporphyrin : Ci 6 H 18 N 2 



which suggests that haematoporphyrin is a di-oxy-phyllopor- 

 phyrin. If this view is correct, it should be possible to trans- 

 form the one into the other, either by reduction of haemato- 

 porphyrin [or by oxidation of phylloporphyrin. It was 

 eventually found that both porphyrins furnished the same 

 derivative on complete reduction. This is haemopyrrol (methyl- 

 propyl-pyrrol) — 



CH 3 .C 

 HC 



C.CH,.C 2 H S 

 CH 



NH 



and was obtained in 1901 by Nencki and Zaleski, from 

 haematoporphyrin, and a little later by Nencki and Marchlewski 

 from phylloporphyrin. 



The relationship of the animal and vegetable respiratory 

 pigment was thus for the first time clearly established. The 

 presence of the pyrrol ring in these pigments also suggests a 

 relationship to the proteins, in which E. Fischer has demon- 

 strated the presence of the pyrrolidine ring. 



A further result of the work of the Russian investigators was 

 that the final reduction product of both blood and plant pigment, 

 haemopyrrol, was easily transformed on exposure to air into 



1 See Marchlewski, Die Chemie des Chlorophylls. 



