MELANINS. 843 



true of the melanoids produced from proteins en cleavage with acids 

 (SAMUEL Y J ) yield indol or skatol and a pyrrol substance on fusion 

 with alkali, while hippomelanin, according to v. FURTH and JERUSALEM, 

 gives a fecal odor on this treatment, but does not yield any indol or skatol. 

 More characteristic than the two last mentioned bodies is a phenol-like 

 substance, which occurs to a slight extent, and gives a bluish-black 

 color with ferric chloride (v. FURTH). 



The cyclic complexes of the proteins are rightly considered as the 

 mother-substance of the melanins (SAMUELY and v. FURTH and others), 

 and this view has received support by the behavior of tyrosine with 

 oxidases. It has been found that by the action of a plant oxidase, 

 BERTRAND'S tyrosinase, 2 upon tyrosine, colored products and then 

 melanin-like substances are formed, v. FURTH with SCHNEIDER and 

 PRIBRAM, GESSARD, NEUBERG, DEWITZ and others 3 have shown that 

 similar-acting tyrosinases also occur in the animal kingdom, in insects 

 and sepia, in melanotic tumors and in pigmented skin, and v. FURTH 

 and JERUSALEM have prepared an artificial melanin from tyrosine which 

 shows great similarity to hippomelanin. Finally NEUBERG and JAGER* 

 have also prepared extracts from melanotic growths which formed a dark- 

 brown pigment from adrenalin. As indicated above, we tend more and 

 more to accept the view that the melanins are derived from the cyclic 

 components of the proteins. 



In addition to the coloring matters of the human skin it is in place here to 

 treat of the pigments found in the skin or epidermal formation of animals. 



The beautiful color of the feathers of many birds depends in certain cases on 

 purely physical causes (interference-phenomena), but in other cases on coloring 

 matters of various kinds. Such a coloring matter is the amorphous reddish- 

 violet turacin, which contains 7 per cent copper and whose spectrum is very similar 

 to that of oxyhsemoglobin. It must be remarked that according to LAIDLAW 5 

 turacin or at least a pigment with the same properties can be obtained on boiling 

 hsematoporphyrin in dilute ammonia with ammoniacal copper solution. KRUKEN- 

 BERG 6 found a large number of coloring matters in bird's feathers, namely zooery- 

 thrin, zoofulvin turacoverdin, zoorubin psittacofulvin, and others which cannot be 

 enumerated here. 



Tetronerythrin, so named by WURM, is a red amorphous pigment which is 

 soluble in alcohol and ether, and which occurs in the red warty spots over the eyes 

 of the heathcock and the grouse, and which is very widely spread among the 

 invertebrates (HALLIBURTON, DE MEREJKOWSKI MACMUNN). Besides tetronery- 



1 Hofmeister's Beitrage, 2. 



2 Compt. Rend., 122. 



8 The literature can be found in v. Furth and Jerusalem, Hofmeister's Beitrage, 

 10. 



4 Neuberg, Virchow's Arch., 192; Jager, ibid., 198. 



5 Journ. of Physiol., 31. 



6 Vergleichende physiol. Studien, Abth. 5, and (2. Reihe) Abth. 1, 151, Abth. 2, 1, 

 and Abth. 3, 128. 



