204 



BACTERIA, YEASTS, AND MOLDS 



the milk pail during the milking ; (5) bacteria from the 

 hands and clothing of the milker. 



The number of bacteria found even in fresh milk is 

 extremely great, particularly if the milk be drawn without 

 special precautions for cleanliness. Thousands and even 

 hundreds of thousands are sometimes found in each cubic 

 inch. These ^ ^mm- 



I 





■f^v 



. -■*. 



bacteria grow 

 rapidly, inasmuch 

 as milk is warm 

 when drawn 

 from the cow, 

 and by the time it 

 reaches the con- 

 sumer in the city 

 the milk is likely 

 to contain these 

 microorganisms 

 in incredible 

 numbers. The 

 exact numbers, 

 however, are mat- 

 ters of no special 

 importance to us, for fortunately most of the bacteria in 

 milk are harmless. Some of them, indeed, are useful, and, 

 while occasionally troublesome bacteria get into milk, as a 

 rule we may look upon the milk bacteria as doing no injury 

 to the health of the person drinking it (Fig. 6"]). 



Effect of Bacteria upon the Milk. But the housewife 

 is interested in the effect of the growth of bacteria upon 

 the milk itself. The bacteria which grow most rapidly in 



Fig. 66. Milk as seen under the microscope, show- 

 ing numerous bacteria, a, common lactic acid 

 bacteria ; b, gas-forming bacteria ; c, strepto- 

 cocci, causing mastitis ; d, fat globules ; e, a cell. 



