TYPES OF BACTERIA FOUND IN MILK 161 
unsatisfactory, so that the swelled cheese may be practically 
worthless. ‘These organisms have been the cause of the loss of 
enormous amounts of money to cheese makers. In butter-making 
they are not-so disastrous, but here, too, their presence is unde- 
sirable, for they sometimes produce unpleasant flavors in the 
Fic. 32:—Curds from two lots of milk soured by a gas-forming and a 
: non-gas-forming bacterium. 
creams, resulting in an inferior grade of butter. This type of 
organism, therefore, is décidedly the dairyman’s foe. 3 
Several varieties of bacteria belong to this general type of gas- 
producing organisms. Among them are organisms of the B. coli 
type, which are very similar to B. aerogenes, except that they are 
motile. They are inhabitants of the intestine (see page 140), 
and are very:commonly found in milk. 
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