356 THE FORMATION OF MELANINS 



the mode of formation of the natural pigments common to 

 the body in health and disease? Some of these questions 

 we have endeavored to answer by the following experimental 

 work. 



Formation of Melanin from Antialbumid. In view of the 

 somewhat noticeable parallelism in composition between an- 

 tialbumid and the melanins, attention was first directed to 

 the possible formation of a pigment of this class by hydroly- 

 sis of antialbumid. For this purpose a pure antialbumid of 

 known composition was necessary, and since the latter body 

 is prone to slight alteration by too vigorous hydrolysis par- 

 ticular attention was paid to the conditions attending its 

 formation. As the mother substance in the preparation of 

 antialbumid, thoroughly washed coagulated egg-albumin was 

 employed. In the hydrolysis, 2600 grams of the moist coag- 

 ulum, pressed as dry as possible, were heated with 7 liters of 

 3.0 per cent sulphuric acid in a large flask, filled quite to the 

 neck to diminish oxidation, at 100 C. (in a large Arnold 

 sterilizer), for 10 hours. The gelatinous mass of impure 

 antialbumid was thrown upon filters, allowed to drain, and 

 after some washing with water, was transferred to a flask and 

 heated with 3.5 per cent sulphuric acid for 10 hours, after 

 which it was again filtered off and washed with water by 

 decantation and otherwise until the washings were nearly 

 or quite free from acid reaction. To remove any traces of 

 unaltered proteid possibly present, as well as other impuri- 

 ties, the antialbumid was next warmed at 38 C. for 30 hours 

 with an active solution of pepsin-hydrochloric acid (0.2 per 

 cent HC1), the soluble products removed by filtration, and 

 the residual antialbumid washed with water until the wash- 

 ings gave no reaction with the biuret test, nor with silver 

 nitrate for chlorine. The washing was facilitated, after the 

 bulk of the soluble matter had been removed, by carefully 

 adding to the antialbumid suspended in water sufficient dilute 

 solution of potassium hydroxide to make the mixture quite 

 neutral to test paper, thus aiding the removal of any loosely 



