126 BACTERIOLOGICAL EXAMINATION OF WATER. 



Glucose-gelatine. No gas formation. 



Broth. Uniformly turbid. 



Peptone and Salt Solution. No indol reaction produced. 



Milk. Unchanged. 



Nitrate-broth. Nitrites and ammonia produced. 



Litmus-ivhey. Reaction becomes slightly alkaline. 



Microscopical Characters. Thin motile rod varying greatly 

 in length. It does not form spores and grows best at from 

 20 to 24 C. It is decolorised by Gram's method of 

 staining. Involution forms are often seen. 



Proteus Zenkeri. 



Gelatine Plates. The surface colonies are yellowish- white, and 

 from the margin processes extend in every direction, so that the 

 whole colony somewhat resembles a mould. Under a low power 

 many of the processes may be seen to be beaded ; others are 

 spiral, and join with processes from neighbouring colonies. 

 The gelatine is not liquefied for a long time, and then it is only 

 slightly marked. Zoogloea forms are said not to be seen in 

 the depth. 



Gelatine-streak. Along the streak a white growth appears, 

 from which fine processes run out on both sides to the margin 

 of the gelatine ; often the branches are curved with the con- 

 cavity upwards. 



Gelatine-stab. A white surface growth, with processes 

 running out to the margin ; along the stab a white growth 

 appears, from which numerous hair-like branches penetrate 

 horizontally into the gelatine. 



Agar. A thin white growth. 



Potato. Yellowish-white growth. 



Milk. Unchanged. 



Peptone and Salt Solution. No indol reaction produced. 



Glucose-gelatine. No gas formation. 



Microscopical Characters. A thin motile bacillus, varying 

 greatly in length ; some forms are almost like cocci. It does 

 not form spores. It grows best at 20 to 24 C. 



Proteus Mirabilis. 

 Gelatine Plates. The surface colonies, after twenty-four 



