INTRODUCTION XI 



caused the rapid development of our knowledge of micro- 

 organisms in general to be followed with such eager 

 interest by all who had to devote much attention to 

 the sanitary aspects of water-supply. 



The publication by Koch, a little more than ten 

 years ago, of his beautiful and comparatively simple 

 methods of bacteriological study gave an impulse to 

 investigation in this direction throughout the civilised 

 world, and the possibility was at once opened up of 

 approaching the solution of problems connected with 

 water-supply which had long been matters of dispute 

 and speculation amongst hygienic authorities. 



