366 THE FORMATION OF MELANINS 



in. 0.2796 gram substance gave by fusion with NaOH and KNO, 0.0669 gram 



BaSO 4 = 2.79 per cent S. 

 IV. 0.2436 gram substance gave 0.0192 gram ash = 6.11 per cent. 



PERCENTAGE COMPOSITION OF THE ASH-FREE SUBSTANCE. 

 L II. EIL Average. 



C 61.60 ... ... 61.60 



H 8.97 ... ... 8.97 



N ... 10.23 . . . 10.23 



S ... ... 2.98 2.98 



O ... ... ... 21.32 



100.00 



It is thus plainly evident that the melanin obtained from 

 hemipeptone is widely different in chemical composition from 

 the corresponding body obtained from antialbumid. It re- 

 sembles in its content of carbon the melanin-like body pre- 

 pared by Schmiedeberg from Witte's "pepton," but differs 

 widely from it in the amount of both nitrogen and sulphur. 

 It would seem that the artificial melanins differ as widely 

 among themselves in composition as the natural melanins 

 obtainable from melanotic tumors, etc., or from normal 

 pigmentary deposits. Certainly the contrast between the 

 melanoidic acid with its 66 per cent of carbon obtained by 

 Schmiedeberg from serumalbumin and the corresponding pig- 

 ments with 54, 58, and 61 per cent of carbon respectively 

 obtained by us from antialbumid and hemipeptone, is very 

 striking. 



Reactions of the melanins. The pigments formed in the 

 manner described above were practically insoluble in water, 

 although, as stated, the sample obtained from hemipeptone 

 was somewhat soluble when freshly precipitated. They were 

 likewise insoluble in alcohol, ether, chloroform, etc., but readily 

 soluble in exceedingly dilute alkaline fluids. They thus differ 

 in some slight degree from the pigment isolated by Abel and 

 Davis * from the negro's skin. Further, these pigments seem- 

 ingly retain their solubility in dilute alkalies in greater degree 

 than the pigments described by Abel and Davis or the melan- 

 oidic acid prepared by Schmiedeberg f from serum-albumin. 



* Abel and Davis, Journal of Experimental Medicine, 1896, i, p. 386. 



t Schmiedeberg, Archiv f . Exper. Pathol. u. Pharmakol., 1897, xxix, p. 66. 



