312 BACTERIOLOGY 



Litmus milk. . Decolorized ; casein dissolved ; alkaline. Indol negative. 



Grow at 36°. 

 Milk. Not coagulated. 

 Habitat. Water. 



II. Ps. coliserea (Wright) 



B. coktEreus Wright : I.e., 464. 



Morphology. Bacilli of medium size, siiort, ends rounded, in pairs and 

 filaments. Flagella polar. 



Gelatin colonies. Deep : round — oval, granular, brownish, sharp ; later a dark 

 brownish tint in the adjacent gelatin; colonies sometimes moruloid. 

 Surface: round, elevated, grayish, becoming thicker, denser, and papil- 

 late in centre ; microscopically, granular, yellowish brown in centre, 

 becoming sunken in the gelatin and crimpled. 



Gelatin slant. Growth slightly wrinkled, grayish white, lining a furrow in 

 the gelatin. 



Agar slant. Growth elevated, grayish white, translucent, glistening. 



Bouillon. Turbid, with a wrinkled membrane ; becoming clear. 



Potato. Growth elevated, granular, the color of the medium. 



Litmus milk. Decolorized, viscid ; coagulated ; alkaline, becoming brownish. 

 Indol negative. But slight growth at 36°. 



Habitat. Water. 



12. Ps. centrifugans (Wright) 



B. centrifugans Wright : I.e., 462. 



Morphology. Bacilli of medium size, in pairs and filaments. Flagella polar. 



Gelatin colonies. Deep : round, dark, granular, with a greenish shimmer, 

 soon surrounded by a zone of liquefied gelatin. Surface: in 24-48 

 hours, round, crateriform, 3 mm., turbid, flocculi in centre ; micro- 

 scopically granular, a circulating motion ; margin fringed with short hairs. 



Gelatin stab. Liquefaction saccate, a pellicle, greenish below and alkaline. 



Agar, slant. Growth translucent, glistening, grayish, thin, becoming brownish 

 to greenish brown. 



Bouillon. Turbid ; a slight pellicle ; later a brown green tint. 



Potato. Growth thick, spreading, gray-pinkish ; sometimes a rough granular 

 surface. 



Litmus milk. Coagulated, decolorized, amphoteric — acid. Indol produced. 

 Nitrates not reduced. Grow at 35°-36°. 



Habitat. Water. 



