BACTERIA OF MILK AND ITS PRODUCTS 313 



whey. If one patron brings infected milk to a creamery and 

 then another takes away the milk or whey which contains 

 these organisms in the same cans in which they bring their milk 

 the next morning, infection is likely to be distributed and may 

 become widespread. 



Blue Milk. Epidemics of blue milk sometimes occur. 

 This is due to the growth in the milk of a bacterium that pro- 

 duces a blue coloring substance. An epidemic of this kind 

 was described and shown to be communicated from one lot of 

 milk to another as long ago as 1838, by Steinhoff. 



Red Milk. Milk sometimes appears red or bloody, due to 

 the growth of certain bacteria in it. B. prodigiosus some- 

 times gets into the milk from the air and produces there its 

 characteristic red color. A yeast is widely distributed in the 

 air which produces 

 a reddish pink color. 

 These changes of 

 course are to be 

 sharply different!- 

 ated from the pres- 



, FIG. 61. Bacteria producing milk faults, (i) B. 

 ence Of blood in the cyan0 genus (blue milk). (2) B. lactorubefaciens 



milk. In the latter (red milk) - ^ 3) Coccus lactis viscosi ( r( w milk ). 



After Lipman. 



case the red color 



appears immediately upon milking, while in the former it 

 only results from the growth of bacteria, and hence would 

 appear only after a period of incubation of a greater or less 

 length (Fig. 61). 



* iX VV$) 



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