THE CLASSIFICATION OF BACTERIA 319 



Agar slant. Growth glistening, limited, slate-blue, becoming gray. 

 Bouillon. Clouded, whitish flocculi, and a few bluish flocculi on the surface, 



or a bluish ring. 

 Potato. Growth slate-blue, dense, becoming dirty brown. 

 Litmus milk. Coagulated, decolorized ; serum bluish. 

 Glucose gelatin stab. A fair growth ; no gas. Indol produced. Grow at 



36°. The species seems subject to considerable variations, and may be 



identical with, or a variety of, B.jaiithinus. 

 Habitat. Water. 



25. Ps. indigofera (Voges) 



B. iniigoferus Voges : Centralblatt f. Bakteriol., XIV, 1893, 307. 



Morphology. Bacilli 0.6-1.8 /x; occur singly. A polar flagellum. Not 



stained by Gram's method. Grow at 37° 

 Gelatin colonies. Flat, spreading, iridescent, blue. 

 Gelatin stab. Surface growth flat, glistening. 

 Bouillon. A delicate membrane of a blue color. 

 Agar slant. Growth dark blue. 

 Potato. Growth greenish blue. Non-pathogenic. Pigment soluble in HjSO^ 



(brown) ; in HNO., (yellowish) ; in HCl (bluish). Addition of NH^HO 



has no effect on the pigment. 

 Habitat. Water. 



26. Ps. Berolinensis (Classen) Migula 



B. Berolinensis-indlcus Classen; Centralblatt f. Bakteriol., VII, 1890, 13. 



Morphology. Bacilli slender, with rounded ends, like B. typhosus ; occur 



singly, in pairs, in threes, or in packets. The bacillus is surrounded by 



a delicate capsule. 

 Gelatin colonies. Grayish white punctiform, becoming indigo-blue ; borders 



irregular, typhoid-like, colorless. 

 Gelatin stab. On the surface, growth punctiform, deep indigo-blue, slowly 



spreading; contour irregular. The color does not penetrate into the 



gelatin. 

 Agar slant. Growth thick, moist, glistening, deep indigo-blue. 

 Potato (acid). Growth deep blue; on alkaline potato it is dirty green, 



glistening. 

 Bouillon. Turbid, with flocculent particles; no color produced. Do not 



grow at 37°; grow best at 15°. 

 Habitat. Water. 



