146 BACTERIOLOGICAL EXAMINATION OF WATER. 



Agar-plate Cultures. The colonies are more or less circular 

 in shape, greyish-white in colour, and have a moist glistening 

 appearance. 



Agar-stab Culture. There is growth all down the stab ; gas 

 bubbles may form in the medium ; on the surface the growth is 

 like a surface colony. 



Agar-streak Culture. A greyish-white moist glistening growth. 



Potato Culture. A slimy, thin, yellowish-white growth. 



Broth. Abundant, diffuse, cloudy growth. 



Litmus-milk. The opaque bluish-purple coloured fluid is 

 changed into semi-transparent reddish-coloured fluid. If clotting 

 occurs, it is imperfect in character as possibly casein is dissolved 

 as soon as it is 'formed. 



Indol Reaction. Usually no indol is formed in broth cultures, 

 but in one such culture kept for twelve days a feeble reaction 

 was obtained. 



Reduction of' Nitrates. Rapid reduction of nitrates to nitrites 

 in twenty-four hours at 20 C. 



Microscopical Appearances. Small bacillus with rounded ends, 

 solitary, 1 in pairs, or sometimes in short chains; involution 

 forms may be seen. It is actively motile, possesses a single 

 flagellum, and does not form spores. The original culture 

 grew better at 20 C. than at 37 C. 



Remarks. This organism differs from Proteus vulgaris; it 

 has been called sewage Proteus, owing to its prevalence in 

 sewage and its superficial resemblance to the members of the 

 Proteus group. Some of the cultures isolated from sewage 

 were pathogenic to guinea-pigs ; others grew well at 37 C. 



Bacillus Frondosus. 



Isolated from London crude sewage. 



Gelatine-plate Cultures. The surface colonies appear as white 

 coarsely-granular films of irregular shape, which send out curious 

 processes of varied form, resembling bits of sea- weed flattened 

 out. Liquefaction is slow and is shown by slight pitting near the 

 centre of each colony. The deep colonies are not characteristic. 

 Under a low power the superficial colonies have a laminated 

 appearance, and show at the spreading edge processes of most 

 varied shapes, which form patterns of great delicacy and beauty. 



