SUGAR IN" THE NUTRIENT MEDIUM. 127 



soluble in ether, carbon bisulphide, benzol, and chlo- 

 roform. 



The large majority,* in the dry condition, are 

 colored bluish-green by concentrated sulphuric acid 

 and red or orange by caustic potash, or they retain 

 these colors when so treated. But the various pig- 

 ments show various chemical differences and quite a 

 different reaction in the spectrum. The majority 

 may be placed unhesitatingly in the large group of 

 lipochromata which are widely distributed in the 

 animal and vegetable kingdoms, and to which belong 

 the coloring matter of fat, yolk of the egg, the carotin 

 of carrots, and many others. 



Entirely different from these substances are the 

 pigments of bacterium prodigiosum and bacterium 

 kiliense. These take a brownish-red color with con- 

 centrated sulphuric acid, and a yellowish-brown 

 and yellowish-red color with caustic potash. They 

 are allied to one another but still quite distinct, f It 

 has often been assumed, especially on account of the 

 golden shimmer of the prodigiosum culture, that we 

 have to deal here with a coloring matter resembling 

 fuchsin, but on careful examination the resemblance 

 is found to be very superficial. 



Yiolet Pigments. Bacterium violaceum and bac- 



* Thirteen red and fourteen yellow bacteria were examined, 

 and the only exceptions were bacterium prodigiosum and bacte- 

 rium kiliense. Schneider furnishes full tabulated statements 

 concerning the reactions of the alcoholic solution and of the dry 

 coloring matter with various agents, and also concerning the 

 spectrum reactions. 



f The fact that this coloring matter or one of its derivatives is 

 not entirely insoluble in water is evident from the fact that in 

 old agar cultures garnet-red pigment is diffused in the agar. 



