THE CLASSIFICATION OF BACTERIA 173 



Gelatin stab. After 3 weeks, a thin, yellowish expansion on the surface ; in 



depth, small colonies. 

 Agar slant. Grows at 35, yellowish. 

 Potato. No growth. 

 Bouillon. A white cloudy deposit. 

 Habitat. Isolated from Berlin drain water. 



CLASS VII. CHROMOGENIC. WITHOUT ENDOSPORES. AEROBIC 

 AND FACULTATIVE ANAEROBIC. PRODUCE PIGMENT ON GEL- 

 ATIN AND AGAR. PIGMENT REDDISH. 



I. Gelatin liquefied. 



A. Bacteria stained by Gram's method. 



138. Bact . pyocinnabareum (Kruse). 



B. Not stained by Gram's method. 



1. Milk coagulated. 



a. Litmus milk blue or decolorized, reaction alkaline or neutral. 



* Nitrates reduced to nitrites ; pepton-rosolic acid solution 



unchanged. 



139. Bact. erythrogenes (Grotenfelt). 

 ** Nitrates not reduced to nitrites. 



140. Bact. exiguum (Wright). 



b. Litmus milk rendered acid. 



* Growth salmon pink. 



141. Bact. epsilon (Dyar). 



** Growth brownish red or dark orange-red. 



142. Bact. zeta (Dyar). 



2. Milk not coagulated. 



a. Litmus milk rendered acid. 



143. Bact. delta (Dyar). 



b. Litmus milk not reddened, reaction unchanged or alkaline. 



* Pigment bright red or pinkish. 



144. Bact. hamatoides (Wright). 

 144 a. Bact. amylovorum (Burrill). 



** Pigment brownish red. 



145. Bact. rubidum (Eisenberg). 



II. Gelatin not liquefied. 



A. Gelatin colonies filamentous to floccose. 



146. Bact. ferrugineum (Dyar). 



