190 PHARMACEUTICAL BACTERIOLOGY 



effective means of preventing the transmission of infectious diseases such 

 as tuberculosis, typhoid fever, diphtheria, scarlet fever, etc., commonly 

 spread by milk. 



Disadvantages. a. Pasteurization promotes carelessness on the 

 farm and dairy, etc. (This may be controlled by proper regulations, 

 inspections and laboratory examinations.) 



b. Pasteurization renders milk less .digestible. (While it is generally 

 conceded that boiled milk commonly induces constipation, the majority of 

 the evidence plainly indicates that pasteurization has little, if any, effect on 

 the digestibility of the milk.) 



c. Pasteurized milk favors the production of rickets and scurvy. 

 (There is no proof to this effect and authorities agree that the danger is 

 slight; and, further, that it may readily be obviated.) 



d. By destroying the non spore-bearing bacteria, pasteurization some- 

 times allows toxic organisms to grow and produce serious poisons in the 

 milk. (On the other hand, these same poisons are more frequently pro- 

 duced in milk that has not been pasteurized, and thus danger may be 

 obviated in pasteurized milk by cooling it quickly, keeping it cold and 

 shortening the time for distribution.) 



e. Pasteurization is inefficient as a preservative; the milk keeps only 

 twelve to twenty-four hours longer than otherwise. (This is really no 

 disadvantage, for the quicker bad milk sours, the better.) 



/. Pasteurization injures the taste of the milk. (This is not so, if 

 properly done.) 



g. Pasteurization increases the cost of the milk. (True, but it is the 

 cheapest safeguard, and the expense of pasteurization is offset by the 

 keeping quality of the milk.) 



Rosenau has made extensive tests to determine the thermal death- 

 point of those pathogenic microbes most commonly found in milk. His 

 conclusions are summarized as follows: 



Milk heated to 60 C. and maintained at that temperature for two 

 minutes will kill the typhoid bacillus. The great majority of these 

 organisms are killed by the time the temperature reaches 59 C., and few 

 survive to 60 C. 



The diphtheria bacillus succumbs at comparatively low temperatures. 

 Oftentimes it fails to grow after heating to 55 C. Some occasionally sur- 

 vive until the milk reaches 60 C. 



The cholera vibrio is similar to the diphtheria bacillus regarding its 

 thermal death-point. It is usually destroyed when the milk reaches 

 55 C.; only once did it survive to 60 C. under the conditions of the 

 experiments. 



The dysentery bacillus is somewhat more resistant to heat than the 



