68 BACTERIOLOGICAL EXAMINATION OF WATER. 



and the gelatine is slowly liquefied. In gelatine-stab there is a 

 white growth on the surface, which later assumes a violet colour ; 

 the gelatine is slowly liquefied ; there is very little growth along 

 the line of inoculation. On agar there is a yellowish-white 

 growth, which later acquires a violet colour. On potato 

 there is a marked violet-coloured growth. Milk is not coagu- 

 lated. Nitrates are rapidly reduced to nitrites. It is a motile, 

 medium sized bacillus, which does not form spores. 



B. Violaceus Laurentms. 



Isolated by Jordan from the Lawrence. In gelatine plates 

 the colonies in the depth are round and coarsely granular ; on 

 coming to the surface they grow out into thin irregular expan- 

 sions and the gelatine is almost immediately liquefied ; a round 

 violet spot appears in the centre surrounded by cloudy, liquefied 

 gelatine. In gelatine-stab the medium is rapidly liquefied 

 along the inoculation line ; the liquefied gelatine has a violet 

 colour, and there is a dark violet precipitate at the bottom of 

 the tube. On agar and potato there is an abundant growth of 

 a dark violet colour, which soon becomes jet black. In milk 

 there is a rapid growth, the milk acquires a violet colour and is 

 coagulated. In broth there is only a very poor growth, but in 

 nitrate-broth there is a luxuriant growth with formation of a 

 rich violet colour. It reduces nitrates to nitrites rather slowly. 

 It is a short, slight, very motile bacillus, which does not form 

 spores. It often occurs in pairs and chains. 



B. Lividus. 



Found by Zimmermann in Chemnitz water. It closely re- 

 sembles the B. Janthinus ; but the bacillus is non-motile and 

 forms spores. The colonies in gelatine plates have an irregular 

 margin and resemble a Liver acinus. 



B. Violaceus Berolinensis. 



Found rather commonly in Spree water by Plagge and 

 Proskauer and C. Frankel. The same bacillus was also found 

 by Frankland in the Thames and deep-well water. The colonies 

 enclosed in the gelatine appear as small air-bubbles, which have 



