214 On Melanin [Dec. 



hypothesis of a second chromogen appears the more probable, inas- 

 much as in a cross between red haired (no granules) and dark 

 haired individuals (granules present) all of the offspring are dark 

 haired, and granules appear in the hair hiit the diffuse red colora- 

 tion is also present being masked by the darker pigment (see 

 Davenport). 



IV. CONCLUSIONS 



1. All available data indicate that the formation of melanin is 

 brought about by the interaction of an oxidase and an oxidizable 

 chromogen. 



2. Melanins are of at least two types which may be differentiated 

 by their solubility or insolubility in dilute acids. 



3. Those melanins which are soluble in dilute acids are of a 

 protein nature and for this type the name melano-protein is sug- 

 gested. It appears probable that these melano-proteins are not 

 present as granules, but that they are " dissolved " in the keratin 

 structure. 



4. The melanins which are insoluble in dilute acids are of an 

 unknown Constitution, and are, probably, the " pigment granules " 

 which may be seen in the hair and tissues. It is probable that they 

 are formed by the oxidation of a different chromogen from that 

 ivhich yields the melano-proteins. 



5. The protein portion of the melano-protein molecule is readily 

 <decomposed by the action of alkalis or acids, and colored products 

 •are obtained which are not soluble in dilute acids. 



6. Tyrosin, lysin and arginin have been identified among the 

 hydrolytic products of a melano-protein. 



7. Sodium hydroxide Solution decomposes the melanin molecule, 

 and causes a loss of both nitrogen and hydrogen. As many differ- 

 ent products as may be desired, can be obtained by varying the 

 strength of the alkali employed. 



V. BIBLIOGRAPHY 



Bertrand (1896). Sur une nouvelle oxydase ou ferment soluble oxy- 

 dant d'origine vegetable. Compt. rend. acad sei., cxxii, p. 1215. 



Davenport (1909). Heredity of Hair Color in Man. Amer. Nat., 

 xliii, p. 193. 



