72 THE MILK QUESTION 



spite these precautions the milk contained a surprisingly 

 large number of bacteria. Sedgwick and Batchelder in 

 1892 found that, with moderate precautions on the part 

 of the milker, the number of bacteria in fresh milk may not 

 exceed 500 to 1000 per cubic centimetre. Similar results 

 were obtained by a number of other investigators. Von 

 Freudenreisch, in 1902, thought that it would be easy to 

 carry out strict asepsis and thus obtain bacteria-free milk, 

 but he soon came to the conclusion that this was impossible. 

 He found the bacterial content of the mixed milk of twenty- 

 eight cows, obtained with exacting precautions, varied 

 from 65 to 680 micro-organisms per cubic centimetre. 



From the examples quoted we see that it is practically 

 impossible to obtain bacteria-free milk in large quantities, 

 but it is comforting to know that the organisms in carefully 

 collected milk from a healthy animal are not ordinarily 

 harmful. 



Where do these bacteria come from? Our common sense 

 tells us that the mammary glands do not secrete bacteria; 

 they secrete milk. We would expect to find milk freshly 

 drawn from the udder with careful aseptic precautions to 

 be germ free. It is, therefore, a surprise to know that milk 

 is usually contaminated before it comes into the outer 

 world. It is plain that the bacteria may squirm or grow up 

 the milk duct of the teat into the milk cistern. Once hav- 

 ing reached the milk cistern they there find perfect condi- 

 tions for rapid development; a nice, warm, cozy, dark home 

 with an abimdance of food — all the conditions neces- 

 sary for germ development. In truth, the bacteria mul- 

 tiply in the milk cistern and that is why the fore milk, or 

 the first milk which is obtained from the cow, is always 

 much richer in bacteria than the mid-milk or the strip- 

 pings. In good dairy practice the fore milk is always dis- 

 carded. 



Sometimes the bacteria invade the deeper portions of 

 the gland and may even be found in the alveoli. 



