241 



impure water, exposing to germ-laden air, etc.) Within cer- 

 tain limits, the greater the number of bacteria per c.c. of milk, 

 the greater the acidity of the milk. Hence a test for the acid- 

 ity of the milk will give a more or less definite idea of the 

 degree of bacterial infection, and this will suggest the clean- 

 liness or uncleanliness of the milking and of the handling of 

 the milk thereafter. The temperature at which the milk 

 is kept and the age of the milk must always be taken into 

 consideration in drawing the conclusion as to the dairy clean- 

 liness or uncleanliness. As a rule, any acid test showing a 

 higher per cent, of acidity than .07 is due to lactic fermenta- 

 tion. 



Test for Acidity of Milk. "20c.c. of milk is measured 

 into a pDrcelain casserole; a few drops of an alcoholic phen- 

 olphtalein solution are added, and a soda solution (n/10) is 

 dropped in slowly from a burette until the color of the milk 

 remiins uniformly pinkish on agitation. Ic.c. of n/10 alkali 

 corresponds to .009 grams of lactic acid, or to .045 per cent, 

 when 20c.c. are taken."* 



Farrington's alkaline tablet test may be used more readily 

 and conveniently.! 



A test for cleanliness or uncleanliness in milking and in 

 handling milk may be more definitely determined by a bacte- 

 riological examination ; this will determine the number of 

 bacteria per cubic centimeter and the various kinds of bacte- 

 ria in the milk. 



Bacteria in Milk. 



The first few streams of milk drawn from the udder con- 

 tain bacteria; the remainder of the milk may ccme frcm the 

 udder free of germs; but it soon becomes contaminated by 

 mixing with the first milk, by dust, dirt, hair and other parti- 

 cles from the cow's udder and skin ; from the hands and clothes 

 of the milker ; from the air ; from the unclean milk vessels ; 

 and from the impure water used in washing the milk vessels 

 ^nd used in fraudulently adulterating the milk. When the 



* Fanington and Woll's Testing Milk, p. 195. 



t Farriugton and Woll's Testing Milk, pp. 99-105. 



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