the eelation of microorganisms to milk 369 



Sources of Microorganisms in Milk 



The sources from which bacteria get into the milk have been th^ sub- 

 ject of much investigation during the past few years, until now the chief 

 sources of contamination are pretty well understood. These sources 

 may be grouped in a general way under the following heads: 



FiQ. 126. — Vertical section of one quarter of udder showing teat, milk cistern, and 

 larger milk micts. (After Ward and Hopkins.) 



Inierior of the Cow's Udder. Healthy Udders— -MUk as it is 

 secreted by the normal udder of a healthy cow is probably free from 

 bacteria. It is very difficult, however, to obtain milk from the udder 



24 



