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CHAPTER IV 



THE BACTERIAL CONTENTS OF VARIOUS WATERS 



Before proceeding to apply the bacteriological methods 

 to the investigation of the various processes of purifica- 

 tion to which water is submitted on the small as well 

 as on the large scale, thus endeavouring from the 

 biological point of view to obtain some information as 

 to the value of such different kinds of treatment, it 

 will be necessary to gain some general idea of the 

 numbers of micro-organisms which are to be found in 

 waters derived from different sources. We may mention, 

 however, that a large amount of additional information 

 concerning the bacterial contents of various kinds of 

 water will also be found in Chapter V. 



As long ago as the year 1871 Burdon Sanderson^ 

 showed conclusively that both filtered and unfiltered 

 water, ice-water obtained from the purest ice, and even 

 distilled water which had not been recently prepared 

 contained bacteria. The method of investigation pur- 

 sued consisted in introducing these several kinds of 

 water into flasks containing sterilised Pasteur's solution: 

 if the solution subsequently became turbid it was con- 

 cluded that bacteria were present; whilst if, on the other 

 hand, they remained clear, the inference was of course 

 made that no bacteria were contained in the liquids 



^ * The Origin and Distribution of Microzymes in Water and the Cir- 

 cumstances which Determine their Existence in the Tissues and Liquids 

 of the Living Body.' Thirteenth Eeport of the Medical Of&cer of the 

 Privy Council, reprinted in the Quarterly Journal of the Microscopical 

 Society^ October 1871. 



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