MELANINS. 841 



Melanins. This group includes several different varieties of amorphous 

 black or brown pigments which are insoluble in water, alcohol, ether, 

 chloroform, and dilute acids, and which occur in the skin, hair, chorioidia, 

 in sepia, in certain pathological, formations, and in the blood and urine 

 in disease. From the true native melanins we must differentiate the 

 humus-like products obtained on boiling proteins with mineral acids 

 and which have been called melanoidins or melanoidic acid (Schmiedeberg) 

 and whose relation to the true melanins is still unknown. 



The melanoidins are readily soluble in dilute alkali while the melanins 

 show a different behavior in this regard. Of the melanins a few such as 

 SCHMIEDEBERG'S sarcomelanin, and that from the melanotic sarcomata 

 of horses, the hippomelanin (NENCKI, SIEBER, and BERDEZ), which are 

 soluble with difficulty in alkalis, while others, such as the coloring matter 

 of certain pathological swellings in man, the phymatorhusin (NENCKI and 

 BERDEZ) are readily soluble in alkalies. The melanins, as above stated, 

 are in general insoluble in dilute mineral acids; from black sheep- 

 wool GORTNER l has isolated a melanin which was soluble in acetic acid 

 and in dilute mineral acids (see below). 



Among the melanins there are a few, for example the choroid pig- 

 ment, which are free from sulphur (LANDOLT and others) ; others, on the 

 contrary, as sarcomelanin and the pigment of the hair (SIEBER) are rather 

 rich in sulphur (2-4 per cent), while the phymatorhusin found in cer- 

 tain swellings and in the urine (NENCKI and BERDEZ, K. MORNER) is 

 very rich in sulphur (8-10 per cent). Whether any of these pigments, 

 especially the phymatorhusin, contains any iron or not is an important 

 though disputed point, for it leads to the question whether these pigments 

 are formed from the blood-coloring matters. 



According to NENCKI and BERDEZ the pigment, phymatorhusin, isolated by 

 them from a melanotic sarcoma did not contain any iron, and according to them 

 is not a derivative of haemoglobin. K. MORNER and later also BRANDL and L. 

 PFEIFFER found, on the contrary, that this pigment did contain iron, and they 

 consider it as a derivative of the blood-pigments. The sarcomelanin (from a sar- 

 comatous liver) analyzed by SCHMIEDEBERG contained 2.7 per cent iron which 

 was partly in organic combination and could not be completely removed by 

 dilute hydrochloric acid. The sarcomelanic acid prepared by SCHMIEDEBERG 

 by the action of alkali on this melanin contained 1.07 per cent iron. The sar- 

 comelanin investigated by ZDAREK and v. ZEYNEK also contained 0.4 per cent iron. 

 Recently WOLFF 2 prepared two pigments from a melanotic liver, of which one 

 was no doubt modified. The other, which was soluble in a soda solution, con- 



1 Gortner, Journ. of biol. Chem., 8, and Bioch. Bulletin, 1, 1911. 



2 Zdarek and v. Zeynek, Zeitschr. f. physiol. Chem., 36; Wolff, Hofmeister's Beitrage, 

 5. The literature on the melanins may be found in Schmiedeberg, " Elementarformeln 

 einiger Eiweisskorper, etc." Arch. f. exp. Path. u. Pharm., 39; also in Robert, Wiener 

 Klinik, 27 (1901), and Spiegler, Hofmeister's Betrage, 4, and especially v. Fiirth, 

 Centralbl. f. allg. Path. u. Path. Anat., ,15, 1907, 617. 



