PREFACE 



The rapidly growing interest in home economics is caus- 

 ing this subject slowly to assume the aspect of an exact 

 science. At the present time it is becoming necessary 

 for those expecting to become housewives to understand 

 at least the elementary phases of a number of sciences, 

 most prominent among which are chemistry and bacteri- 

 ology. The relation of microorganisms to household affairs 

 has only been recognized in the last few years, but is 

 now felt to be one of the most important phases in the 

 study of the problems of the household. The present 

 work is therefore designed for all interested in household 

 affairs, including not only students of household econom- 

 ics but all persons who have practical charge of homes 

 and are interested in keeping them in the best and most 

 healthful condition. 



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