CHAPTEE II. 



SOURCES OF INFECTION IN THE STABLE, AND ITS 

 PREVENTION. 



ON its arrival at the dairy the milk is always more or 

 less infected with bacteria, it being impossible to pro- 

 tect it entirely from infection in practical dairying. This 

 is apparent from the mere fact that it is not always possi- 

 ble to keep the milk sterile even when all precautions of 

 a scientific investigation are taken. Lister's experiments 

 concerning the original sterility of milk form an interest- 

 ing illustration of this matter ; although the greatest pre- 

 cautions were taken, he obtained only a very few milk 

 samples that would keep as long as the milking was done 

 in the stable. If the milking, on the other hand, took place 

 in the open air, the experiments were nearly always suc- 

 cessful. It would therefore seem that the air in the cow- 

 stable at the time of these experiments was so mixed with 

 bacteria that in spite of all care it proved almost impossi- 

 ble for him to protect the milk from infection. 



It is therefore evident that the milk already in the 

 barn must be highly infected with bacteria in its ordinary 

 handling. It is, however, out of the question to introduce 

 scientific, exact means of precautions in the practical work 

 in the barn, in order to prevent all infection of the milk, 

 as this would make the work too complicated and expen- 

 sive, and some of the precautions that would have to be 



