THE CLASSIFICATION OF BACTERIA 175 



Pepton-rosolic acid solution. Unchanged. 

 Habitat. Red milk, water, faeces of a child. 



Variety. B. erythrogenes-rugatus (Dyar). "Differs from the preceding, 

 in that the growth on agar is thin, membranous, and wrinkled ; " Dyar, 

 I.e., 374. 



140. Bact. exiguum (Wright) 



B. exiguus Wright : I.e., 447. 



Morphology. Bacilli small, rounded ; occur singly and in pairs and clumps. 



Gelatin colonies. Deep-, round to oval, with greenish centres and granular 

 margins. Surface: round, pinkish, translucent disks; microscopically, 

 granular; centres pink, lighter toward margin, becoming liquid and 

 salmon-pink. 



Gelatin stab. Liquefaction crateriform ; pinkish sediment. 



Agar slant. Growth thin, moist, pinkish. 



Bouillon. Turbid ; white sediment. 



Potato. Growth spreading, moist, glistening, reddish yellow. 



Litmus milk. Coagulated, decolorized, slightly peptonized, amphoteric. 



Glucose-bouillon. No gas. Indol slight. A strong development at 35-36. 



Habitat. Water. 



141. Bact. epsilon (Dyar) 



B. epsilon Dyar : I.e., 369. 



Morphology. Bacilli 0.5 : 0.7-1.0 it. 

 Agar slant. Growth translucent, pink. 

 Milk. Coagulated, at least on boiling. 

 Pepton-rosolic acid solution. Unchanged. 

 Habitat. Air. 



142. Bact. zeta (Dyar) 



B. zeta Dyar : I.e., 369. 

 Morphology. Bacilli 0.5 : 0.7-1.0 li. 



Gelatin. A slight development ; liquefaction does not begin before 10 days. 

 Milk. On the surface, a red cream. On solid media, as above. Nitrates not 



reduced to nitrites. 

 Habitat. Air. 



143. Bact. delta (Dyar) 



B. delta Dyar: l.c., 368. 



Morphology. Bacilli 0.5 : 0.8-1.0 ti; occur singly or in short chains. 

 Gelatin. Liquefied, beginning in 21 days. 

 Agar slant. Growth thin, red. 



