PREFACE TO SECOND EDITION 



Since the appearance of the first edition of this work 

 the investigation of various phases of the bacteriology of 

 water has been advanced with zeal by many workers on 

 both sides of the Atlantic. As a result a considerable 

 mass of new evidence has accumulated which has estab- 

 lished the bacteriological examination of water on a 

 firmet basis than ever, and shown it to be the most direct, 

 accurate and practical method at the disposal of the 

 sanitarian. 



The study of presumptive tests for the colon bacillus 

 has advanced, with highly satisfactory results. The 

 methods for the isolation of specific pathogenic organ- 

 isms have also been notably improved. 



An excellent volume on Water Bacteriology by Dr. 

 W. G. Savage has appeared during the past year, which 

 shows the English methods of investigation and interpre- 

 tation to be closely in accord with those used in America. 



It has been our aim in preparing this new edition to 

 include the results of the work of the last four years 

 which bear on the practical investigation of sanitary 

 questions connected with water supply. Considerable 

 additions have been made to the treatment of the prob- 



