128 ATLAS OF BACTERIOLOGY. 



terium janthinum were found to contain a violet 

 coloring matter, which was insoluble in water, readily 

 soluble in alcohol, but insoluble in ether, benzol, and 

 chloroform. In the dry state it is turned yellow by 

 concentrated sulphuric acid and emerald green by 

 caustic potash. In alcoholic solution it assumes a 

 greenish to bluish-green color on the addition of 

 strong acids and ammonia. The pigment loses its 

 color on the addition of zinc and sulphuric acid. 



Claessen and Schneider examined, in a very imper- 

 fect manner, the beautiful blue coloring matter of 

 bacterium indigonaceum Claessen. This pigment is 

 insoluble in the ordinary solvents; in hydrochloric 

 acid it gives at first a blue, then a yellowish-brown 

 solution. Other acids dissolve it but cause decom- 

 position. Caustic potash gives a bluish-green color. 



Distinct from these blue coloring matters is the 

 blue pigment formed by bacterium syncyaneum (blue 

 milk) in addition to bacterio-fluorescein (vide below) 

 and for which I propose the term syncyanin. Thumm 

 describes the pigment as very unstable. Acids color 

 it steel blue ; in slight acidity it is bluish-black, neu- 

 tral black, and alkaline brownish-black. 



According to the recent investigations of Thumm 

 the fluorescent pigments, which are found in numer- 

 ous cultures, are all identical. The coloring matter, 

 for which I propose the term bacterio-fluorescein, is 

 lemon yellow and amorphous in the dry state, soluble 

 in water and dilute alcohol, and insoluble in strong 

 alcohol, ether, and carbon bisulphide. The watery 

 solution, when concentrated, has an orange color, 

 when diluted, a pale yellow color; with acid reaction 

 it shows no fluorescence, with neutral reaction a 



