534 



Yellow Fever 



(Fig. 154). It is actively motile and has flagella. It does 

 not form spores. 



Staining. It stains by the usual methods, but not by 

 Gram's method. 



Cultivation. The bacillus can be grown upon the usual 

 media. It grows readily at ordinary room temperatures, 

 but best at 37 C. 



Colonies. Upon gelatin plates it forms rounded, trans- 

 parent, granular colonies, which during the first three or 

 four days somewhat resemble leukocytes. The granular 

 appearance becomes continuously more marked, and usu- 



Fig. 154. Bacillus icteroides (Sanarelli). 



ally an opaque central or peripheral nucleus is seen. In 

 time the entire colony becomes opaque, but does not liquefy 

 gelatin. 



Gelatin. Stroke cultures on obliquely solidified gelatin 

 show brilliant, opaque, white colonies resembling drops of 

 milk. 



Bouillon. In bouillon it develops slowly, without either 

 pellicle or flocculi. 



Agar-agar. The culture upon agar-agar is said to be 

 characteristic. 



The peculiar and characteristic appearances of the colonies 

 do not develop if grown at 37 C. ; but at 2o-22 C. the 



