Kands of Milk Fermentatious. 69 
be found in the milk the bacteria of any germ dis- 
ease with which the animal may be afflicted, or which 
may be carried into the milk through the atmosphere, 
the water used in cleansing utensils, or the persons 
of individuals suffering from the disease. 
The fermentations of milk.—The normal fermenta- 
tions to which milk is subject may he conveniently 
divided into three classes. First, those which feed 
upon and cause changes in the milk-sugar, known as 
lactic fermentations. Second, those that feed upon 
and cause changes in the albuminoids of the milk ; 
these in turn are of two classes, peptogenie and pu- 
trefactive. Third, those which attack the fats, and 
are known as butyric fermentations. Besides these, 
which may be called normal fermentations, in that 
they will easily occur in any sample of milk if left to 
itself, there are a large number of other fermentations 
which may be called abnormal, from the fact that 
they oceur only in isolated localities, or from time 
to time. These abnormal fermentations include one 
which causes the casein of milk to coagulate without 
the development of lactic acid, known as sweet curd- 
ling; another which causes a peculiarly ropy or slimy 
condition of certain constituents of milk; still an- 
other that results in the formation of an intensely 
bitter product in the milk; an aleoholie fermenta- 
tion, and several fermentations which result in the 
production of various colors, collectively known as 
chromogenic fermentations. An illustration of this 
class is seen in the well-known ‘‘bloody bread,’”’ 
which is caused by the growth of Bacillus prodigiosus,. 
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