190 The Story of the Bacteria 



ease-producing powers, sewage-polluted water 

 from wells, or springs, or rivers, or lakes, ought 

 not to be used for drinking and culinary pur- 

 poses without some system of purification 

 which is demonstrably efficient. 



The new methods of bacterial analysis of 

 water, which have been described in the earlier 

 pages of this book, can give a clue sometimes 

 as to whether or not a given water has actually 

 been polluted with sewage, or human or animal 

 waste, and especially whether the modes of 

 purification to which it has been subjected, 

 either naturally or artificially, have actually 

 been efficacious in removing the living germs. 

 But intelligent inspection of the sources is 

 usually better than any laboratory analysis 

 in determining whether a water is improperly 

 polluted. 



It is thus evident that upon the intelligence, 

 knowledge, and fidelity, of the authorities 

 largely rests the responsibility of pure water 

 supplies for cities and towns, and the house- 

 holder is to a large degree at the mercy of 

 these officials, so far as his protection against 

 the acquirement of bacterial disease, especially 



