1,52 BACTERIOLOGICAL EXAMINATION OF WATER. 



Gelatine-streak. -A delicate granular film of limited extent 

 forms on the surface of the gelatine. After some days the 

 film changes its appearance, and shows numberless fine processes 

 radiating outwards and upwards from the central line. Tuft- 

 like processes also extend into the solid gelatine. Liquefaction 

 slowly sets in and shows itself as a longitudinal furrow. 



Gelatine-shake Cultures. No gas formation. The gelatine 

 is slowly liquefied. 



Agar-streak. In twenty-four hours at 37 C. a dirty yellowish- 

 white film has covered nearly the whole oblique surface. The 

 spreading edge may extend as irregular processes, forming leaf- 

 like patterns. Later, the film darkens in colour and becomes 

 wrinkled. 



Potato Cultures. The growth is extremely characteristic. At 

 37 C. in twenty-four hours the whole surface of the potato is 

 covered with a thin, yellowish-white film, which has a character- 

 istic, folded, wrinkled appearance. The substance of the potato 

 takes on a bright pink colpur. Later, the film becomes thicker, 

 more deeply pitted and wrinkled, and the colour becomes brown. 



Broth. In twenty-four hours at 37 C. a greyish-white 

 wrinkled film is formed at the surface, and the liquid below is 

 nearly quite clear. 



Litmus-milk. In seventy-two hours a weak clot has formed 

 and the liquid near the surface is semi-transparent. On shaking 

 the tube a pinkish tinge develops. 



Indol Reaction. No indol is formed. 



Nitrate-broth. Great reduction of nitrates to nitrites in 

 twenty-four hours. 



Microscopical Appearances. Long bacillus with rounded ends, 

 solitary, and in pairs and long chains. It is actively motile, 

 possesses numerous flagella, and forms spores. It grows very 

 rapidly at 37 C. 



Remarks. This bacillus appears to be identical with B. mesen- 

 tericus ruber. 



Bacillus Mesentericus (Sewage variety I.). 



Isolated from London crude sewage. Gelatine-plate cultures 

 heated to 80 C. for ten minutes. It is constantly present in 

 sewage in the form of spores. 



