60 BACTERIOLOGICAL EXAMINATION OF WATER. 



liquefies the gelatine ; the upper part in the dark has a red 

 colour, but in the light is colourless. On agar and potato it 

 produces a yellowish layer, and around this there is a slightly 

 yellowish-red colour. Milk is coagulated and peptonised by 

 lab-ferment ; it is at first reddish-brown in colour and finally 

 blood-red. 



B. Rubefaciens. 



Found by Zimmermann in water. It is a slender very motile 

 bacillus. The colonies in the depth are small, round, and have 

 a yellowish or brown colour ; on the surface they form flat 

 expansions which do not liquefy the gelatine, and have a sugges- 

 tion of a red colour. In gelatine-stab it forms a greyish-white 

 layer on the surface ; the gelatine itself has a bluish-white colour 

 which later becomes a light wine-red. On agar it forms a thick 

 bluish-grey expansion. On potato there is a yellowish or brown 

 layer, and the potato assumes a flesh colour. 



B. Lactericius. 



Described by Adametz as the "ziegelrother" bacillus which he 

 isolated from water. It is a bacillus three to five times as long as 

 broad. It is not motile and does not form spores. It does not 

 liquefy gelatine, and on the surface forms a thick brick-red layer; 

 there is very little growth in the stab. On potato it forms a 

 brick -red layer. 



B. Rubescens. 



Found in canal-water by Jordan. It is a slightly motile large 

 bacillus, which does not form spores. The colonies on the 

 surface are thick porcelain-white drops, which later become 

 brownish in colour ; in the depth the colonies are small. The 

 gelatine is not liquefied. In gelatine-stab there is a porcelain- 

 white nail-head projection on the surface, but only slight growth 

 along the stab. On agar there is a white growth, which later 

 becomes wrinkled, and in about three weeks a pinkish tinge is 

 seen. On potato there is a rapid growth, at first brown, but 

 slowly changing to pink ; in three weeks there is a luxuriant 

 flesh-coloured growth. Milk is not coagulated, and eventually 

 assumes a pinkish tinge at the surface. It does not reduce 

 nitrates. 



