142 BACTERIA IN MILK. 



ination. If dry hay or other dry food is thrown down in front of the 

 cattle, a large amount of dust will arise and spread through the air 

 of the stable. Such dust is crowded with bacteria, many of which 

 are alive and will settle into the milk-pail during milking. The 

 common practice of keeping cattle in the same room where they 

 are milked is thus very productive of a large source of bacterial 

 contamination. 



The Milker. Of late years it has become evident that the 

 bacteria coming from the milker or other persons in the dairy are 

 among the most serious. This is not so much because of the 

 number of bacteria that may enter the milk from this source, but 

 because of their types. In ordinary dairies the milker rarely makes 

 any special toilet before milking, but is liable to perform this task in 

 old, soiled clothing, with no attempt at cleaning his hands and face. 

 Under these circumstances, while, so far as concerns numbers, he is 

 not so great a source of bacteria as the cow, some of these organisms 

 are sure to fall from his hands or clothes into the milk-vessels, 

 especially if he adopts the filthy habit of wet milking. The number 

 of bacteria from such a source is, probably, not great, and does not 

 add materially to the bacterial content. But in one respect these 

 bacteria assume a more important significance. The bacteria 

 which produce diseases in one animal do not necessarily produce 

 diseases in other animals. Those which produce diseases in cattle, 

 with some exceptions (tuberculosis), do not usually have the same 

 effect on man. But it is evident that any disease germs that may be 

 present in one man are just the kind that can develop in any other 

 human being. Therefore, bacteria contamination from human 

 sources is more dangerous to other human beings than any infection 

 from animals. For this reason the bacteria which enter the milk 

 from the milker are liable to be more dangerous than those which 

 come from any other source. 



TYPES OF BACTERIA FOUND IN MILK. 



Many different types of bacteria get into milk from these various 

 sources. Some of them are useful, some are of no particular signifi- 



