PREFACE. vii 



others) have been pioneers in the development of this 

 new field in sanitary science. To gather the results of 

 their work together in such form as to give a correct 

 idea of the best American practice is the purpose of 

 this little book; and this we have tried to do, with such 

 completeness as shall render the volume of value to the 

 expert and at the same time with such freedom from 

 undue technicality as to make it readable for the layman. 

 It should be distinctly ' understood that students using 

 it are supposed to have had beforehand a thorough 

 course in general bacteriology, and to be equipped for 

 advanced work in special lines. 



The Biological Laboratories, 



Mass. Institute of Technology, 



Boston, March 10, 1904. 



