PASTEURIZATION OF MILK. 161 



renewed infection before it is consumed. To prevent this 

 infection, which is a very important point in case of baby- 

 feeding, the milk must be heated and kept in a sterile and 

 carefully closed vessel. Many different kinds of apparatus 

 and methods have been invented for the treatment of milk 

 for this purpose. I shall here only mention two methods 

 which may be considered typical. The one was invented 

 by Dr. Engli-Sinclair in Switzerland; the other by Dr. 

 Soxhlet in Germany. Both these methods are essentially 

 alike : Engli-Sinclair works with simpler and more primi- 

 tive apparatus than Soxhlet. Both methods seem to give 

 perfectly reliable results, although the admirers of the 

 Soxhlet method maintain that that alone fulfils the de- 

 mands for an ideal milk-sterilizing apparatus. 



Methods of " Milk-sterilization." * The method of 

 Engli-Sinclair is as follows : In an ordinary porcelain-lined 

 iron casserole provided with a cover a sheet-iron stand is 

 placed holding seven bottles; these will hold about 1. 6 liters 

 (1| quarts), or about as much milk as is required for one 

 meal. The bottles are filled with milk of the best quality, 

 which if necessary is diluted with water; the bottles are at 



* There is some confusion in the use of the term sterilization and 

 pasteurization of milk and milk products. Sterilization, as we have 

 seen, implies absolute freedom from bacteria, while pasteurization 

 implies relative freedom from bacteria; the former is reached by 

 prolonged heating at the boiling-point or higher temperatures; the 

 latter by heating at temperatures from 165-1S5 F. (see p. 159). 

 When the methods to be described in the above were given to the 

 world, it was thought that the product obtained was absolutely germ- 

 free, and the process was therefore called sterilization of milk a name 

 still applied, although according to our present knowledge it is not 

 strictly correct. The methods are described in the present chapter 

 because the milk thus treated will act like pasteurized milk, as will 

 be apparent from the remarks of the author. W. 



