100 MODERN DAIRY PRACTICE. 



by starting the bad-smelling butyric fermentation ("ran- 

 cidity"). These two processes the lactic and butyric 

 fermentation seem to be coherent to such an extent that 

 a German author (Wigand) recently even asserted that the 

 butyric fermentation is simply a continuation of the lactic- 

 acid fermentation (" ein weiteres Stadium der Milchsaure- 

 galirung "). 



IV. Bacteria Injurious to the Milk. Bacteria of very 

 different kinds and of highly- varying characteristics belong 

 to this group. In order more readily to obtain a general 

 view of them, we will separate them into the following sub- 

 divisions : 



1. Bacteria producing acidity in the milk. 



a. Bacteria producing lactic fermentation. 

 5. Bacteria producing butyric fermentation. 

 c. Bacteria producing volatile acids in the milk. 



2. Bacteria producing no acidity in the milk. 



a. Bacteria causing coagulation of the casein. 



"b. Bacteria causing coagulation of the casein and 



subsequent peptonization of the coagulum. 

 c. Bacteria bringing the casein into fermentation 



without coagulating it. 



We shall below briefly mention the main bacteria in- 

 cluded under the preceding divisions. 



la. Lactic Fermentation. There are many kinds of 

 bacteria producing lactic fermentation. Most of them 

 belong to the bacteria proper, while others belong to the 

 yeasts. The lactic-acid bacteria will be described more 

 fully under the " Ripening of the Cream." 



Besides the lactic-acid bacteria proper, a number of 

 other bacteria may be included under this division which 

 only incidentally produce fermentation. Certain infec- 



