PASTEURIZATION OF MILK. 165 



found sufficient to reduce the virulence of the tubercle bacilli 

 which are in the milk so as to render them harmless. It 

 follows from this that, although the tubercle bacilli in milk 

 are not absolutely destroyed by a pasteurizing temperature, 

 they are rendered less harmful. Hence pasteurizing has two 

 advantages. It removes from the milk the danger of the 

 distribution of contagious diseases, and it accomplishes this 

 in such a way that the pasteurized milk, after cooling, can 

 hardly be distinguished from fresh milk. Lastly, the milk 

 does not keep long and must be used fresh, thus avoiding the 

 above mentioned danger occasionally experienced in old 

 sterilized milk in which the bacteria have not been wholly 

 killed. 



It is believed also that pasteurization reduces the likelihood 

 of milk being a cause of the diarrheal diseases. Inasmuch as 

 we do not positively know the bacteria which produce these 

 troubles, it is difficult to say how pasteurization of milk 

 actually affects them. Pasteurization greatly reduces the 

 number of bacteria in the milk, destroying the larger part of 

 the lactic bacteria and many of the peptonizing and putre- 

 fying class. The milk is, therefore, freer from bacteria and, 

 perhaps for this reason, less liable to produce intestinal trou- 

 bles. If the diarrheal troubles are produced by toxic pro- 

 ducts in the milk, and a sample of milk is old so that the bac- 

 teria have had a chance to gro.w and produce in it their toxic 

 products, it is hardly likely that the pasteurization can have 

 an influence upon the poisons themselves, and thus wholly 

 remove the danger of intestinal troubles. Pasteurization 

 could be a remedy only for such troubles as are due to 

 the actual growth of bacteria in the intestinal tract. But the 

 best proof of the utility of pasteurization is the result. It 

 has been found from a large amount of experience that such 

 treatment of milk does have a marked tendency to reduce 

 diarrheal troubles among children, and that cases of intestinal 

 diseases yield much more readily to treatment if the milk is 



