FROM THE PRACTICAL VIEWPOINT 



the lengths of time for holding, which in the labo- 

 ratory tests have been found to be effective, be 

 somewhat increased, in commercial practice. 



Various cities have made regulations in this re- 

 spect which appear to best suit local conditions. 

 In New York City, when regulations were first 

 adopted concerning milk pasteurization, the length 

 of time for which milk must be held when heated 

 to 158 F. was officially fixed at no less than three 

 minutes, and if heated to 140 it must be held for 

 at least twenty minutes. Between these extremes 

 of temperature holding times were fixed which va- 

 ried between three minutes and twenty minutes. 



Experiments were made by Schores and Rose- 

 nau * in which careful tests were carried on while 

 milk was being pasteurized in the ordinary way, 

 a commercial pasteurizer and holding device being 

 used. These tests were made for the purpose of 

 determining if the thermal death point of patho- 

 genic bacteria, as indicated by laboratory tests, 

 could be safely relied upon under commercial con- 

 ditions. In their experiments the investigators in- 

 troduced germs of tuberculosis, diphtheria, and 

 typhoid fever, into milk, which was then run 



*The Journal of Medical Research Vol. XXVI NO. 1. 

 25 



