.162 DENITRIFICATION 



Nitrate Bouillon. Turbid in twenty-four hours; denitrification 

 and frothing in two to three days. 



Bact. centropunctatum, Jensen. Isolated from cow dung and 

 faeces of guinea-pig. On agar under aerobic conditions is coccus- 

 like, .3 to .5 p in diameter, with a large slimy capsule 3 p, dia- 

 meter. In nitrate bouillon is rod-shaped, motile, and like Bact. 

 Stutzeri. Under anaerobic cultivation are large, oval organisms 

 5 p long, i fM thick, which stain chiefly at the ends. On 

 account of thick capsule is difficult to stain unless washed in 

 xylol and alcohol first on cover slip. 



Gelatine. Not liquefied. Surface colonies thin, whitish trans- 

 lucent, ragged borders ; deep colonies, small white entire border. 

 Stab beaded, with white spreading growth on surface. 



Agar. Surface colonies thick, moist, not slimy, dirty grey in 

 colour. 



Nitrate Bouillon. Turbid in one to two days, with frothing 

 and denitrification. 



Bact. Schirokikhi, Jensen. A feebly, motile, aerobic organism, 

 isolated from horse dung. Rods with rounded ends, usually three 

 or four together in a chain when grown in bouillon ; in pairs on 

 solid media. Spores are abundant, and produced in two days. 



Gelatine. Liquefied to a pale bluish liquid in which are yellow 

 grains. Surface colonies are slow in developing ; on the third 

 day, at 20 C., are about i to 2 mm. in diameter, in five days or less 

 colonies run together. Stab ; rapid, funnel-shaped liquefaction, 

 liquid pale grey at first, yellowish afterwards, with sediment. 



Agar. Surface colonies develop sooner than on gelatine, and 

 are star-shaped in twenty-four hours at 37 C, with a raised centre 

 surrounded by pale blue rays. In three or four days the colonies 

 become rounded, 2 to 4 cm. in diameter, with a yellowish brown 

 zone round each. 



Potato. On alkalinized potato (.05 Na 2 CO 3 ) growth is light 

 brown. 



Nitrate Bouillon. (25 per cent. KNO 3 ). Denitrification com- 

 plete in five to eight days, at 30 to 35 C. 



