CHAP, xii MELANINS 581 



varies also, and melanins free from iron as well as others containing 

 high percentages of iron have been described. A great deal of attention 

 was paid to the iron-radical, because it was hoped to get some in- 

 formation as to whether melanins were derived from the blood pigments. 

 Inasmuch as most cell-albumins and all the nucleo-proteids contain 

 iron, no definite conclusions can be formed regarding this question. 



Being amorphous, melanins offer no guarantee of having been freed 

 from all remains of blood pigments, albumin, etc., and therefore the 

 presence of small amounts of iron is of no value in throwing light on 

 their origin ; but, on the other hand, two groups of melanins may be 

 distinguished by containing either a very high or a very low sulphur- 

 percentage. 



Most of the investigations regarding melanin have been made on 

 tumours. Pigments from cases of human melanotic sarcomata, mostly 

 metastases of the liver, have been investigated, apart from the older 

 . inquiries, by Berdez and Nencki, 1 who use the term phymatorhusin ; 

 by Morner, 2 Miura, 3 Brandl and Pfeiffer, 4 Hensen and Nolke, 5 

 Schmiedeberg, 6 Zdanek and v. Zeynek, 7 and v. Zumbusch, 8 and 

 Wolff. 9 Berdez and Nencki, 10 and Nencki and Sieber, 11 have also 

 analysed the c hippomelanin,' a pigment they obtained from the mela- 

 notic tumours of a white horse. 



The black colouring-matter of the hair and the skin of negroes 

 has been studied by Sieber, 12 Nencki and Sieber, 13 and Abel and Davis; 14 

 that of the choroid by Scherer, 15 Sieber, 12 and Landolt. 16 The melanin 

 from the ink-bag of Sepia has been analysed by Nencki and Sieber. 13 

 In the following table the analytical numbers which Schmiedeberg 

 gives for melanoidins have been included. 



1 J. Berdez and M. Nencki, Archiv f, experiment. Pathol. u. Pharm. 20. 346 

 (1885). 



2 K. A. H. Morner, Zeitschr. f. physiol. Chem. 11. 66 (1886) ; 12. 229 (1887). 



3 M. Miura, Virchow's Archiv, 107- 250 (1887). 



4 J. Brandl and L. Pfeiffer, Zeitschr. f. Biol. 26. 348 (1890). 



5 H. Hensen and Nolke, Deutsches Archiv far Jdin. Medizin, 62. 347 (1899). 



6 0. Schmiedeberg, Archiv f. experiment. Pathol. und Pharm. 39. (1897) (see 

 also the index). 



7 E. Zdanek and R. v. Zeynek, Zeitschr. f. physiol. Chem. 36- 493 (1902). 



8 L. v. Zumbusch, ibid. 36. 510 (1902). 



9 H. Wolff, Hofmeister's Beitrage, 5. 476 (1904). 



10 J. Berdez and M. Nencki, Arch./, exper. Path. u. Pharm. 20- 346 (1885). 



11 M. Nencki and N. Sieber, ibid. 24. 17 (1888). 



12 N. Sieber, ibid. 2O. 362 (1885). 



13 M. Nencki and N. Sieber, ibid. 24. 17 (1888). 



14 Abel and Davis, Journ. Exper. Med. 1. 361 (1896). 



15 J. Scherer, Liebig's Ann. 40. 1 (1841). 



16 H. Landolt, Zeitschr. f. physiol. Chem. 28. 192 (1899) ; here the older literature. 



