RELATION OF BACTERIA TO DAIRY PRODUCTS 555 



case of certified milk, and the success of the efforts put forth is 

 evidenced by the record which this milk has made; but the 

 methods necessary to safeguard milk sufficiently in this way 

 are expensive and, under our present conditions, do not seem 

 to be applicable to the milk supply of large cities. For such 

 supplies, the second method, namely, the treatment of the milk 

 after production, is doubtless the only method available at the 

 present time. The method employed for this purpose is that 

 known as "pasteurization," which means that the milk is 

 heated in such a way as to kill any disease-producing organisms 

 which may be in it. By this method the milk is heated for a 

 definite length of time at a definite temperature. 



Pasteurization of milk 1 



The value of pasteurization from a sanitary standpoint is 

 of the greatest importance when market milk is under con- 

 sideration. 



In the first place, the pasteurization of milk, when the process 

 is properly performed, affords protection from pathogenic 

 organisms. Such disease-producing bacteria as Bacillus tuber- 

 culosis, B. typhi, B. diphtheria, and the dysentery bacillus are 

 destroyed, or at least have lost their ability to produce disease, 

 when heated at 140° F. for twenty minutes or more. Although 

 the infective agent in scarlet fever is unknown, epidemics of 

 the disease have been traced to milk supplies, and in such 

 cases pasteurization has been resorted to as a means of safe- 

 guarding the public, with apparently satisfactory results. 



In the second place, pasteurization causes a reduction of the 

 infantile death rate due to the ordinary intestinal disturbances. 

 Numerous experiments definitely prove the value of pasteuri- 

 zation in this connection. While it has not been possible to 

 isolate any special organisms which act as the causative agents 



i B. A. I. Circular No. 184. 



