74 MORPHOLOGY OF THE BACTERIA. 



upon cooked potato, and cultivated by Colin in 

 nutritious solutions. This coloring matter is 

 reddened by acids, and restored to blue by al- 

 kalies, just as that which forms when lichens 

 are macerated in presence of ammonia. 



M. violaceus, Cohn (Bacteridium violaceum, Schroe- 

 ter). 



Violet-blue masses or glairy stains formed of 

 elliptical corpuscles larger than those of M.pro- 

 digiosus, observed first by Dr. Schneider, then 

 by Schroeter on cooked potato. 



Later, Cohn has described the two following 

 new species (1876), which should be included in 

 this group : 



M. Candidas, Cohn. 



Stains and points ichite as snow, observed 

 upon slices of cooked potato. 



M. fulvns, Cohn. 



Little rust-colored drops, consisting of cells, 

 globular or united in pairs, in a tenacious inter- 

 cellular substance, diameter 1.5 ^ observed by 

 Eidam, then by Kirchner, upon horse dung. 



It is also to the genus Micrococcus that we 

 must refer the little globular bacteria, gifted 

 with movement, found by Eberth in white, yel- 

 low, and red perspiration, and by Chalvet in the 

 pus on the edges of certain wounds, but which 

 should not be confounded with the blue color 

 produced by a Bacterium. 



