28 MARKET DAIRYING 
these is blue. It is, however, not often met with in dairy 
practice since the color usually does not appear until the 
milk is several days old. The specific organism that 
causes blue milk has been known for more than half a 
century and is called cyanogenous. Another color that 
rarely turns up in dairy practice is produced by a germ 
known as prodigiosis, causing milk to turn red. Other 
colors are produced such as yellow, green and black, but 
these are of very rare occurrence, 
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Microscopic appearance of pure and impure milk. A, Pure milk ;B, after 
standing in a wash room for a few hours in a dirty dish, showing, besides 
the fat globules, many forms of bacteria.—Moore. 
