I9I4] Alfred P. Lothrop 459 



characters. This correlation I was able to corroborate. In order 

 to test the specificity of this property further, a detailed study of 

 the chemical nature of these pigments was undertaken under the 

 guidance of Prof. Gies. 



Six organisms representing the different genera established by 

 the Winslows were selected as f ollows : 



Albococcus — white pigment 

 Aurococcus — orange pigment 

 Micrococcus — yellow pigment 

 Sarcina lutea — yellow pigment 

 Sarcina aurantiaca — orange pigment 

 Rhodococcus — red pigment. 



These were first grown on a large number of media of different 

 compositions, in the hope of obtaining some clue as to the chemical 

 nature of the pigments f rom the nutrient substances needed for their 

 synthesis. This hope was not realized. Peptone or some soluble 

 protein was essential for pigment production by the cocci. In gen- 

 eral it appeared that Optimum growth conditions were also the most 

 favorable conditions for color formation. Moderate acidity was 

 best. Purin bases and creatin had no effect. Cholesterol had a 

 marked influence on the yellow pigment, which showed a decided 

 greenish tinge during the first f ew days of growth ; it had no effect 

 on the other organisms. Slight variations were observed with 

 other substances but none of them seemed definite or characteristic. 



An attempt to isolate the pigments from the other organic sub- 

 stances was not successful. The quantity obtained is so minute at 

 best, and so easily lost in the purif ying process, that a sufficient amount 

 of the pure material could not be obtained. It was possible, how- 

 ever, to work out a number of the reactions of the pigments studied 

 when they were extracted in a partially pure state, and considerable 

 light was thrown by this procedure upon their mutual relationships. 



The pigments are all soluble in alcohol, ether and Chloroform. 

 They may be precipitated from alcoholic sol. with lead acetate or 

 water. Any such precipitate carries the pigment along with it, but 

 the latter may be re-extracted with alcohol. In the purest State I 

 was able to obtain, the microscopic picture was that of a colorless 

 hyalin film with a number of colored granules distributed more or 

 less irregularly in it. 



