312 Miss F. M. Durham. On the Presence of [Nov. 10, 



were prepared from it. The blackening and formation of black substance 

 occurred as before, but 48 hours in the incubator were required before 

 the action commenced. The same juice was found to have lost its 

 activity when kept for a week. 



Experiments were then made with extracts of skins, which had 

 been kept in alcohol (95 per cent.). The skins were chopped and 

 ground with kieselguhr and distilled water, and pressed out as before. 

 The resulting extract was colourless and cloudy in appearance. When 

 treated with tyrosin and ferrous sulphate, and incubated, the same 

 results were obtained, viz., darkening of the fluid and the formation 

 of a black deposit. The time of action was delayed, so that about 

 10 days were necessary for the change of colour to appear. 



I also tried the skins of black unhatched chickens, which had been 

 kept in 95 per cent, alcohol, and obtained like results from them. The 

 extract from the skins of the chickens was clear and colourless. After 

 the darkening had commenced, I filtered the solution and added more 

 tyrosin, and in this way, I was able to get a further deposit of black 

 substance. 



Solutions were prepared in another way. Juice, which had been 

 obtained from the skins of fresh animals was saturated with ammo- 

 nium sulphate. The resulting precipitate was filtered off, and was 

 then washed with a solution of saturated ammonium sulphate, dissolved 

 in distilled water and re-precipitated by saturation with ammonium 

 sulphate. On re-dissolving this precipitate in distilled water, a certain 

 portion of it was found to be insoluble. This was filtered off and the 

 filtrate was dialysed against distilled water. When free from sulphate 

 (as shown by testing with lead acetate solution), the clear, colourless 

 fluid was treated with tyrosin and ferrous sulphate and incubated. 



As before, pigment was formed, and as in the case of the skins preserved 

 in alcohol, the action was delayed. About 10 days were required. 

 . Amongst other animals tested in this way, I used self-coloured 

 " red " guinea-pigs. I used the f cetal young and also the mother for 

 comparison. The hair of this kind of guinea-pig contains only one 

 pigment, deep yellow or orange in colour. 



In the case of the young guinea-pigs, the solution became yellow 

 and an orange-coloured deposit was formed. I filtered this off, and 

 on the addition of more tyrosin, a fresh orange deposit was obtained. 

 The extract made from the skin of the mother also changed in 

 colour and yielded a yellow deposit, but less in amount than in the 

 case of the young animals. 



Hitherto, material from white or albino animals has yielded no 

 results, but the animals obtained were too few for final conclusions to 

 be formed in regard to them. Up to the present, only minute quantities 

 of the coloured substances have been obtained, insufficient for complete 

 analysis. They resemble melanins in being soluble in alkalis and 





