132 Report of the Bacteriologist of tub 



or not used at all. It should he rememhorod that some of the 

 organisms which are often found in milk will snccessfnlly with- 

 stand hoiling for some hours and the sterilization, in the true 

 sense, of any commercial quantity of milk at a sinjile heating is 

 a practical impossibility unless temperatures above that of boil- 

 ing water are used. 



THE TWOFOLD APPLTCATTOX OF PASTEURIZATION 



TO MILK. 



The subject of the pasteurization of milk has been presented 

 to the American public with reference to two distinct problems 

 — the sanitary milk supply of cities and the production of uni- 

 formly good butter. 



While heat is applied in both cases the methods of application 

 which have been found most successful in each are radically 

 different and an attempt to accomplish either object by the other 

 process has not yet been shown to be practical. The first method 

 is too slow and expensive to be adapted to butter making and the 

 second plan when carried on at a temperature sufficiently high 

 to kill the tubercle bacillus gives an objectionable flavor to the 

 milk. Fortunately this flavor does not remain in the butter. 



THE DISCONTINUOUS OR nOUSEIIOLD SYSTEM. 



About ten years ago when the use of tuberculin was bringing 

 home the alarming prevalence of tuberculosis among our dairy 

 cows and the danger of transmission of the disease to invalids 

 and children through milk seemed self-evident, pasteurization 

 was brought forward as a safeguard from this danger. In this 

 method the milk was heated at a definite temperature for a defi- 

 nite length of time. 



At first 67.3°C. (155°F.) for 20 minutes was advocated, but 

 owing to the change brought about in the viscosity of the milk and 



