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 

 employed in the kitchen who can satisfactorily use a ther- 

 mometer, and it is out of the question to expect any ordi- 

 nary servant to heat milk at a temperature of i6o° for 



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

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



half an hour. The only way it can be accomplished is by 

 some device which will bring about the result in a simpler 

 way. The most convenient 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 to be 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 



