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. hcematoides (Wright). 

 144 a. Bact. amylovorum (Burrill). 



** Pigment brownish red. 



145. Bact. rubidum (Eisenberg). 



II. Gelatin not liquefied. 



A. Gelatin colonies filamentous to floccose. 



1 46 . Bact . ferrugineum ( Dyar) . 



