THE PUBLIC WATER, MILK, AND FOOD SUPPLY 355 



Certified milk. Some dairies sell certified milk. This 

 means that unusual care has been given to all the work in 

 connection with the dairy, and as a result unusually pure 



FIG. 148. Cooling milk. This should be done as soon as drawn. 



milk is obtained. This milk is certified by the inspectors 

 and is sold at a higher price than ordinary milk. But 

 every town should have inspected milk, which means clean 

 milk, at the regular price. 



DEMONSTRATION 28 



Purpose. To compare the cleanliness of milk from different 

 sources by estimating the number of bacteria in a cubic centi- 

 meter (cc.). 



Materials. Several samples of milk. See demonstration 27 

 and read i under Directions. 



