BACILLUS CYANOGENUS 215 



Biological Characters. They are all anaerobic and liquefy gelatine 

 media very quickly, and form gas quickly in sugar-containing media. 

 In Milk, No. II. causes coagulation without putrid gas formation. 

 No. III. has no effect. 

 No. IV. coagulates milk with putrid gas formation. 



Pathogenesis. Nos. III. and IV. are poisonous to animals, while 

 No. II. is not. 



BACILLUS CYANOGENUS (Bacillus of blue milk). 



This organism, the cause of blue-coloured milk, was first cultivated 

 by Hueppe on gelatine plates. 



Microscopical Appearances. -- Bacilli of various dimensions 

 according to Hueppe and Flugge, 0*3 to 0'5 by 1 to 4 p. 



Motility. Motile, the flagella being arranged in a bundle at one 

 end (Lophotricha). 



Spore Formation. Absent. The spores described by Hueppe are 

 considered by Heim as nothing but involution changes. 



Staining Reactions. Stains with the ordinary dyes, but not by 

 the Gram method. 



Biological Characters. Grows best at ordinary room temperature ; 

 at 37 almost no growth takes place. 



On Gelatine Plates. Greyish-white, granular, non-liquefying colonies 

 with scalloped edges. 



In Stab Cultures the deep growth is very limited. 



On A gar. Greyish-blue growth. 



On Potatoes. A yellowish shiny coating. Two pigments are formed, 

 a blue and a fluorescent colour. In gelatine cultures the fluorescence 

 appears first, and later the blue-black pigment. The latter develops 

 more luxuriantly on agar media. 



In Milk the blue pigment is only formed in the presence of an acid. 

 In non-sterile milk blue spots appear at first on the cream ; finally the 

 whole surface is coloured a sky blue. 



In Sterile Milk a grey colour develops, which only turns blue on the 

 addition of an acid. If grape sugar is added to sterile milk it is coloured 

 blue by the bacillus, an acid being formed from the sugar. 



Pathogenesis. Non-pathogenic. 



This bacillus was supposed to cause the blue colour in cheese, but 

 such a supposition is untenable in view of the inoculation experiments 

 conducted by Adametz and Beyerinck. 



