128 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



the milk during the milking process. They are all objectionable in milk 

 intended for direct consumption. Milk in the udder of a healthy cow is 

 both pure and sterile and would remain sweet indefinitely if these organ- 

 isms could be excluded; but since this is impossible the only thing to be 

 done is to reduce their number to a minimum by cleanly methods, and 

 by cold to prevent their increase. Milk is an excellent medium for the 

 growth of bacteria. If special cafe has not been exercised in milking, 

 many bacteria will have gained access to the milk and unless properly 

 cooled will cause its rapid deterioration. The most noticeable of these 

 organisms in milk are those that change the milk sugar into lactic acid, 

 thus "souring" the milk. Milk spoils rapidly when warm because the rate 

 of increase of the organisms present depends upon the temperature, most 

 species developing more rapidly at the temperature at which milk is 

 drawn; but by cooling their development is arrested. It has been shown 

 that at 03 Pahr., some germs increase two-hundred fold in four hours; 

 at 55 Fahr. they will increase only eight-fold in the same length of time, 

 and their activity is almost entirely stopped by still lower temperature. 

 Thus every minute during which milk is left at a warm temperature 

 greatly shortens its keeping quality. Many other species of bacteria are 

 found in milk, causing such changes as blue milk, ropy milk, bitter milk, 

 etc. 



Investigation shows that disease germs, such as those of tuberculosis 

 and typhoid fever, thrive in milk, and may be carried by that medium from 

 place to place. Milk sometimes contains the germs of tuberculosis, com- 

 ing from the cow herself, when she is affected with this disease. Since 

 this is one of the most common diseases in man, and since young children 

 are more susceptible to it than are adults it is very important that the 

 milk supply should be free from these germs. This disease may be de- 

 tected by having the cows tested with tuberculin test. Persons having 

 germ diseases of any kind should not be allowed to care for the cows, or 

 have anything to do about the dairy. 



The aim of the good milk producer is to protect the milk as much as 

 possible from contamination. Not all contamination is sediment and milk 

 may be far from pure even though there is no foreign matter visible to 



