708 EXPERIMENT STATION EECOKD. 



" The averages of two analyses agree with each other remarkably well, with 

 the exceptions that the humin nitrogen from the black wool is 3.45 per cent 

 in excess and the amino nitrogen in the filtrate from the bases is 2.5 per cent 

 less than that in the white wool. The excess of huDiin nitrogen is due to the 

 presence of pigment. There is no necessary relationship between the lack of 

 amino nitrogen in the filtrate from the bases and the excess of humin nitrogen. 

 The nitrogen content of white wool was found to be 16.27 per cent while there 

 is only 15.11 per cent of nitrogen in the black wool." 



The low nitrogen percentage of the black wool is thought probably due to 

 the presence of melanin, which has a lower nitrogen content than the keratin 

 structure. The author has shown that the nitrogen of the melanin which 

 appears in the humin fraction can only be a part of the true melanin nitrogen 

 present in the wool. Apparently, hydrolysis with strong acids breaks down the 

 melanin molecule. This observation is in agreement with previous work. 



On the composition of tyrosinase from two enzym.s, M. "W. Beijeeinck 

 (E. Akad. WetenscJi. Amsterdam, Proc. Sect. Sd., 15 {1912-13), pt. 2, pp. 932- 

 937). — When tyrosinase acts upon tyrosin a substance is obtained which is 

 commonly called melanin. Its color may be jet black, or It may vary between 

 light brown, pure red, brownish red, sepia, and black. The pigment is very 

 stable, resisting heating with strong alkalis and sulphuric acid. Even when 

 boiled with nitric acid, melanin remains almost unchanged. 



Melanin is said to be the pigment present in the hair and hide of the higher 

 animals. The theory is that tyrosin, when acted upon first, yields such products 

 as homogentisic acid, ammonia, and carbon dioxid, and by another oxidation 

 the homogentisic acid is converted into melanin. 



In this work melanin formation was studied in a culture obtained by sowing 

 garden soils on agar plates containing a medium composed of agar 2 per cent, 

 tyrosin 0.1 per cent (dissolved in a few drops of sodium carbonate solution), 

 and 0.02 per cent of potassium acid phosphate at 30° C. After 2 or 3 days 

 numerous little colonies were formed which consisted of Streptothrix (Actino- 

 myces). The common bacteria of the soil do not develop at all or only 

 sparingly on the tyrosin plate and can not under the given conditions compete 

 with the slowly growing Actinomyces. In some of the colonies a jet black spot 

 was found, and near the center of the spot the Actinomyces was always present. 



A more minute observation revealed the fact that the Actinomyces always 

 lies under a thin glassy layer of fine rod bacteria. " This layer covers like a 

 crust the jet black columns of Actinomyces and prevents them from producing 

 spores, which does take place on that part of the mycelium which develops 

 outside the bacterial cover. If from this layer the bacterium is brought into 

 pure culture, which is easily done on broth-gelatin or broth-a^ar plates, it 

 proves to be an extremely delicate polar ciliate rodlet, which forms no spores 

 and strongly liquefies gelatin. Streaks of the pure culture on a tyrosin plate 

 produce no melanin at all, and in this respect the bacterium resembles 

 Actinomyces." 



It is obvious from this that pigment formation results from the symbiosis of 

 these organisms. This was proved by additional experiments. The 2 organisms 

 produce no pigments on peptone or broth-containing media. Several other 

 species of Actinomyces produce blue, red, or yellow pigments. " In this case it 

 is not tyrosin but glucose, malates, and nitrates that form the chromogenous 

 food, so that the symbiosis is then evidently associated with other factors than 

 those active in the production of melanin from tyrosin." 



Experiments made with the Actinomyces and the sodium salts of homogentisic 

 acid gave no pigment, but when the other bacterium was present a brown 



