QUALITATIVE BACTERIOLOGICAL ANALYSIS. 139 



Broth. Soon becomes cloudy, a stringy precipitate, and a 

 thick skin on the surface. 



Nitrate-broth. Reduces nitrates vigorously and rapidly. 



Microscopical Characters. Large, long, stout bacilli, with 

 rounded ends. Usually gathered in short strings. No spore 

 formation observed. About 3'6 to 4 JJL long and T5 /* broad. 

 Highly motile; grow better at 37 C. than at 21 to 23: 

 develop well under a mica plate. 



Bacillus Delicatulus. 



Isolated from the effluents of nearly all the tanks. 



Plate-cultures. When young, whitish, homogeneous, with a 

 regular, radiating edge. In two days the gelatine becomes 

 liquefied; later, the centre becomes darker than the surrounding 

 zone. 



Gelatine-tubes. In two days the gelatine is liquefied well down 

 into the inoculation line. The gelatine is completely liquefied 

 in about seven days. There is a thick whitish skin on the 

 surface, and a heavy, flocculent, brownish precipitate at the 

 bottom. 



Agar-tiibes. At first a crinkly greyish growth which, when 

 older, becomes porcelain- white and glistening. Grows well both 

 on the surface and below. 



Potato-cultures. A grey spreading growth ; not projecting. 



Milk. The milk is coagulated, and gives a strong acid 

 reaction. 



Broth. Soon becomes cloudy. A white precipitate and a 

 white scum. 



Nitrate-broth. Reduces nitrates to nitrites very rapidly and 

 completely. 



Microscopical Characters. Medium-sized, plump bacilli; often 

 joined in pairs and in short strings, 2 /LL long and 1 /LL broad. 

 Spore formation was not observed. V 7 ery motile. Grows better 

 at 37 C. than 21 C. This species is very sensitive to low 

 temperatures ; it refuses to grow at about 15 C. The cultures 

 in tubes appear to live only a short time. 



SEWAGE-BACTERIA DESCRIBED BY LAWS AND ANDREWKS. 

 In 1894 Laws and Andrewes presented to the London County 



