Blue and Red Milk 375 



in pure culture and is designated as Bacillus cijanogenus. 

 It is a rod-shaped organism, a pronounced ae'robe, and 

 is entirely harmless to human beings. It grows readily 

 in milk as well as on potatoes, boiled rice, and vegetable 

 casein. Being sus- 

 ceptible to acid 

 conditions, this or- 

 ganism will not de- 

 velop in sour milk. 

 The pigment pro- 



by it IS Fig 5Q Bacteria producing milk faults. 1. 

 arkliiKl anrl Bacillus cyanogenus (bacillus of blue milk); 



SOlUDIC ana x 26QO (Hinterberger.) 2. Bacillus lac- 



f ^^ ^ 



? / ^* iX \V5) 



F ^^r - \ ^ 



J / , *Qfr / \ ^ 



V I / 

 \S' 



. . - 



erk fiof torubefociens (red milk); X 2,000. (Gruber.) 



SO that, 3 Coccuslactis viscosi (ropy milk); X 2,600. 



notwithstanding 



the restriction of the bacterial growth to the surface, 

 the coloring matter may become diffused throughout 

 the liquid. 



In the presence of other organisms, the character- 

 istic blue pigment may be partly or entirely obscured, 

 although the other changes produced by Bacillus 

 cijanogenus may still remain prominent. Instances are 

 recorded in which the milk fault caused by this organ- 

 ism persisted for years in certain localities. Its elimina- 

 tion was finally effected either by the thorough cleaning 

 of the utensils and premises, or by the inoculation of 

 the fresh milk with sour milk containing vast numbers 

 of the normal lactic-acid bacteria. 



Red milk. The red coloration that gradually de- 

 velops after milk is drawn may be produced by one of 

 several microorganisms. Bacterium prodigiosum and 

 Bacillus lactis erythrogcnes are more prominent than 



