194 BACTERIA, YEASTS, AND MOLDS 



and is nearly as easily digested and assimilated as raw milk ; 

 hence the objections raised against sterilization do not apply 

 to pasteurization. 



On the other hand, there is one practical objection. In an 

 ordinary household it is almost impossible to find one em- 

 ployed in the kitchen who can satisfactorily use a thermometer, 

 and it is out of the question to expect any ordinary servant 

 to heat milk at a temperature of 140° for half an hour. 



Fig. 68. Apparatus for home pasteurization of milk. The figure on 

 the right shows method of cooUng the milk by running water. 



The only way it can be accomplished is by some device which 

 will bring about the result in a simpler way. The most con- 

 venient apparatus for this purpose is that shown in Fig. 68. 

 This consists of a series of bottles which readily fit into 

 cylinders placed in a larger vessel. This receptacle is filled 

 with boiling water, and the bottles, filled with milk, are placed 

 in the cylinders. The whole is set aside to cool. The milk 

 is warmed by the hot water surrounding it, and the water 

 is at the same time cooled by the milk. The size of the 

 vessel is so proportioned to the bottles that, when properly 

 used, the milk is heated to about the temperature desired 



