PREFACE. 



The general awakening of the community to the 

 importance of the arts of sanitation — accelerated by the 

 rapid growth of cities and the new problems of urban 

 life — demands new and accurate methods for the study 

 of the microbic world. Bacteriology has long since 

 ceased to be a subject of interest and importance to 

 the medical profession merely, but has become intimately 

 connected with the work of the chemist, the biologist, 

 and the engineer. To the sanitary engineer and the 

 public hygienist a knowledge of bacteriology is indis- 

 pensable. 



In the swift development of this science during the 

 last ten years perhaps no branch of bacteriology has 

 made more notable progress than that which relates to 

 the sanitary examination of water. After a brief period 

 of extravagant anticipation, and an equally unreason- 

 able era of neglect and suspicion, the methods of the 

 practical water bacteriologist have gradually made their 

 way, until it is recognized that, on account of their deli- 

 cacy, their directness, and their certainty, these methods 

 now furnish the final criterion of the sanitary condition 

 of a potable water. 



