364 THE FORMATION OF MELANINS 



in sulphur (10 per cent), like the phymatorhusin of Berdez 

 and Nencki,* while others, like the choroidal pigment, f are 

 entirely free from sulphur. Again, while the majority of 

 these pigments contain practically no iron at all, others con- 

 tain 0.5 per cent of this element.^ Hence there may be 

 justification for the suggestion made by Brandl and Pfeiffer 

 that the melanins should be divided into groups to be desig- 

 nated as ferro-melanins, sulpho-melanins, etc. The melanins 

 which we have prepared from antialbumid are practically free 

 from iron, the ash containing only the merest trace of this 

 element. Somewhat suggestive is the fact that in both of our 

 experiments with antialbumid, in spite of the difference in the 

 length of the hydrolytic process, the yield of melanin hi both 

 cases amounted to about 5 per cent. 



Formation of melanin from so-called hemipeptone. Having 

 demonstrated the possibility of preparing a melanin-like sub- 

 stance by the hydrolysis of antialbumid, the question naturally 

 arose whether bodies of the so-called hemi class will likewise 

 yield a melanin by hydrolysis. To test this point, so-called 

 hemipeptone formed by the hydrolysis of coagulated egg- 

 albumin with 3 per cent sulphuric acid was employed. The 

 peptone was prepared by using the acid fluid, resulting in the 

 formation of antialbumid. The fluid was neutralized with 

 ammonia, the filtered solution concentrated, and the albumoses 

 separated collectively by saturation of the fluid with ammonium 

 sulphate, after the method suggested by Kuhne.|| After 

 complete removal of the albumoses, the excess of ammonium 

 sulphate was separated by alternate concentration and crys- 

 tallization, after which the last portions of the salt were 

 removed by treatment with barium carbonate-^]" The filtrate, 



* Berdez and M. Nencki, Archiv f. exper. Patbol. u. Pharmakol., 1886, xx, 

 p. 346. 



t Sieber, Ibid., 1886, xx, p. 362. 



| See Brandl and Pfeiffer, Zeitschrift fur Biologie, 1890, xxvi, p. 348. 



Loc. cit. 



|| Kiihne, Zeitschrift fiir Biologie, 1892, xxix, p. 1. 



1 See Chittenden, Mendel, and Henderson, Amer. Jour. PhysioL 1899, ii, 

 p. 173. 



