MILK AND ITS PRODUCTS 153 



the lactic organisms and for this reason milk infected 

 with them sours with great difficulty. 



The action of this class of bacteria is to increase the 

 viscosity of milk, which in mild cases simply assumes a 

 slimy appearance. In extreme cases, however, the milk 

 develops into a ropy consistency, permitting it to be 

 strung out in threads several feet long. 



Slimy or ropy milk cannot be creamed and is therefore 

 worthless in the manufacture of butter. Such milk sliould 

 not be confused with gargety milk which is stringy when 

 drawn from the cow. The bacteria belonging to this class 

 are easily destroyed as they do not form spores. 



3. GASSY FERMENTATION. 



This is an exceedingly troublesome fermentation in 

 cheese making and is also the cause of much poor flavored 

 butter. The gas germs are very abundant during the 

 warm summer months but are scarcely noticeable in 

 winter. Like the bitter germs, they are antagonistic to 

 the lactic acid bacteria and do not grow during the rapid 

 development of the latter. They are found most abun- 

 dantly in the barn, particularly in dung. 



4. TOXIC FERMENTATIONS. 



Toxic or poisonous products are occasionally developed 

 in milk as a result of bacterial activity. They are most 

 commonly found in milk that has been kept for some 

 time at low temperature. 



5. CHROMOGENIC FERMENTATIONS. 



Bacteria belonging to this class have the power of 

 imparting to milk various colors. The most common of 



