NON-PATHOGENIC BACTERIA. 83 



Properties. Very motile ; liquefying gelatine at a tempera- 

 ture of 25 to 30 C., with oxygen and a little moisture, and in 

 the dark, a peculiar electric-blue light develops a phosphores- 

 cence. 



Growth. Slowly ; must have oxygen ; does not grow under 

 10 C. or over 50 C. 



Plates. Little round, gray points, which under low power 

 appear as green colonies with reddish tinge around them c 

 Cooked fish, when smeared upon the surface with a little of the 

 culture, show the phosphorescence most marked. Grows well 

 on potatoes and blood-serum. 



Bacillus Phosphorescens Indigenus. (Fischer.) 



Origin. Waters in the northern part of Germany. It differs 

 from the Indian bacillus, in that it grows at a temperature of 

 5 C., and does not develop upon potatoes or blood-serum. 



Bacillus Phosphorescens Gelidus. (Forster.) 



Origin. Surfaces of salt-water fish. 



Form. Short, thick rods, looking oval sometimes ; zoogloea 

 are often formed. 



Properties. Motile ; does not liquefy gelatine ; a beautiful 

 phosphorescence from the surface of fish ; it can be photographed 

 by its own light. 



Colonies. Grows best between and 20 C. ; grows slowly, 

 and mostly on the surface. The material must contain salt. 

 A bouillon made with sea-water, or 3 to 4 per cent, common 

 salt will suffice. The colonies appear as those of the Phospho- 

 rescens Indicus. 



Fresh herring laid between two plates will often show phos- 

 phorescence in twent}^-four hours. 



The other three varieties require glucose in the culture before 

 they give out any glow. They are Bacterium Pflugeri, Bact. 

 Fischeri, and Bact. Balticum. They do not dissolve gelatine. 



Several very indistinct species, found in waters from factories 

 and in some of the mineral waters, deserve yet to be men- 

 tioned. They have been given various names by observers ; 

 almost a new classification created. Such are the crenothrix, 

 dadothrix, and beggiatoa. 



