NITRATES AND NITRITES 161 



spite of the aerobic character of the organism. When present 

 are white, somewhat transparent and slimy later, with ragged 

 edge. Deep colonies small, rounded, and yellowish white. 

 Stab threadlike, very delicate growth all over surface. 



Agar. Surface colonies are produced on agar; roundish 

 edge ; they are very thin often, with a whitish centre, and from 

 .5 to 3 cm. across. 



Potato. On alkalinized potato (.05 per cent. Na 2 CO 3 ) little 

 growth at room temperature : at 30 C. in two days, dirty brownish 

 red : with shining surface. 



Nitrate Bouillon. Denitrification of nitrate only in presence 

 of B. coli or other reducing organism. Denitrifies a nitrite 

 bouillon alone, with frothing. 



Bact. agile, Amp. and Gar. A facultative anaerobic organism 

 isolated from cow dung; very short, motile rods, i to 1.5 /x long, 

 .1 to .3 ja thick. 



Gelatine. Not liquefied. Surface colonies, round, white, 

 scarcely visible (150 to 170 /x diameter), and grow slowly. In 

 nitrate gelatine small gas bubbles surround them. Stab thin and 

 slightly beaded, with small growth at surface, i mm. diameter, 

 greyish. 



Agar. White, slimy colonies, which remain small. 



Potato. On alkalinized (.05 per cent. Na 2 CO 3 ) potato, 

 growth is very slow, thin, yellow or dirty in brown colour. 



Nitrate Bouillon. Grows well in this medium, denitrifying 

 and producing froth with fine gas bubbles and turbidity. 



Bact. Hartlebii, Jensen. A motile organism isolated from 

 soil. Rods, 2 to 4 ^ long, .75 p thick; stains easily and 

 generally uniformly. 



Gelatine. Not liquefied. Surface colonies very small, i to 3 

 mm. in diameter, slimy, semi-transparent and white, usually with 

 entire border. Stab beaded, with a white slimy growth at the 

 surface, 3 to 6 mm. diameter. 



Agar. Surface colonies slimy, translucent; later more watery ; 

 deep colonies small white and entire. 

 L 



