124 MICRO-ORGANISMS IN WATER 



Thus, on the average, out of every 100 micro- 

 organisms present in the untreated river-water, there 

 were removed by the water companies before distribu- 

 tion in the case of the 



1886 1887 1888 



Thames . . . 97'6 96'7 98-4 micro-organisms 

 Lea (E. London Co.) 96'5 95'3 95'3 



With regard to the removal of this large percentage 

 proportion of the micro-organisms through the treat- 

 ment adopted by the water companies, w r e may appro- 

 priately quote the following words from a paper read 

 by one of us at the York Congress of the Sanitary Insti- 

 tute in 1886 1 : 



' Although the organisms thus removed are probably 

 in general perfectly harmless, it must not be supposed 

 that their removal is of no importance, for it must be 

 remembered that the micro organisms which are known 

 to produce disease, and which are termed pathogenic, 

 do not in any way differ from the ordinary organisms 

 in water so as to render it probable that they would 

 behave differently in the process of filtration ; but, on 

 the contrary, there cannot be any serious doubt that 

 their behaviour under these circumstances would be 

 precisely similar. Now such disease-organisms fre- 

 quently do gain access to water, and it is obviously 

 of the greatest importance to ascertain what sort 

 of impediment this process of filtration, which is so 

 largely practised, offers to their passing on to the 

 consumer.' 



' By means of this bacteriological examination it is 

 thus possible to obtain a far more satisfactory know- 

 ledge of the kind of filtration which water has under- 

 gone than by a mere appeal to the eye of the observer, 



1 ' Filtration of Water for Town- supply,' Percy Frankland. Trans- 

 actions of the Sanitary Institute of Great Britain, vol. viii. 1886. 



