RULES AND REASONS FOR FARM CARE OF MILK. 



101 



blood heat. At this elevated temperature bacterial growth takes place 

 with surprising rapidity, and unless the animal heat is artificially lowered 

 and the milk kept chilled, various fermentations are set up in it as a re- 

 sult of the growth of diiferent bacterial forms. Common experience is so 

 uniformly in accord with this that no further statement is necessary to 

 emphasize its importance. (Figure 6.) 



FERMENTATIONS OF MILK. 



So far we have considered the manner of infection of milk by bacteria 

 rather than the kind of infection. As the biological defects in milk possess 

 more or less well defined characteristics that enable the experienced per- 

 son to recognize them, it is necessary that the leading troubles with which 



PROGENY OF A 



SINGLE GERM 



IN TWELVE HOURS 



FiO. 6. Showing the effect of cooling railk on the growth of bacteria. The beneficial results of 

 early chilling are readily apparent. 



the factory patron may be brought in contact should be so described as to 

 enable him to recognize their presence and intelligently determine the 

 cause of the same. A great deal of misconception exists among dairymen 

 as to the causes of these troubles. We shall attempt, however, to outline 

 briefly the causes of these various defects in milk with sufficient clearness 

 so that they may be recognized. This will enable the patron to intelli- 

 gently search for the same and apply an efficient remedy directly to the 

 seat of the trouble rather than to expend so much well intended but mis- 

 directed energy in other directions. 



SOUR MILK OR LACTIC ACID FERMENTATION. 



Milk, if left to itself invariably undergoes a fermentative change, gen- 

 erally known as souring. The acidity of the same gradually increases un- 

 til finally the amount of acid developed causes a coagulation or precipita- 

 tion of the casein, and milk is said to curdle. This change is brought about 

 mainly by a fermentation of the milk sugar, lactic acid being the chief 

 product formed. The primary cause of this change is not to be found in 

 any atmospheric condition, such as damp or hot weather, or sudden 



