PREFACE 



THIS volume is primarily intended as a practical handbook 

 for those engaged in the chemical and bacteriological exami- 

 nation of milk for public health purposes, but it is also hoped 

 that it will be of material assistance to students and others who 

 have previously assimilated the fundamentals of bacteriologi- 

 cal technique. 



The control of milk supplies was formerly confined to a 

 chemical examination for adulteration, but since the beginning 

 of the 20th century the bacteriological examination has been 

 regarded as a " sine qua non," and in America the present 

 tendency is to have both examinations made under the super- 

 vision of the Public Health Authorities. For this reason no 

 apology is necessary for the inclusion of chemical methods and 

 the data which will enable the examiner to interpret the results 

 obtained. 



In the bacteriological section an attempt has been made to 

 include all methods that have been proved to be reliable and in 

 some instances the details of the standard methods of the 

 American Public Health Association have been given; in other 

 cases the report as published by the A.P.H.A. should be con- 

 sulted. 



The tables of bacteriological results have been added in 

 the hope that they will lead to the standardisation of records. 

 At present the results reported by many laboratories are not 

 comparable because of the form in which they are issued. 



JOSEPH RACE. 

 OTTAWA, ONT., 

 December, 1917. 



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