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DISTRIBUTION OF 'BACTERIA 



of the number of bacteria in different waters may be obtained 

 from the following table : 



NUMBER OF BACTERIA IN VARIOUS WATERS 



The Origin of Bacteria in Water. Some bacteria come 

 from the air, being washed from the sky with the dust. The 

 majority of bacteria get into surface water from soil washings. 

 The number which get in depends upon the conditions sur- 

 rounding a body of water ; for example, a great many more 

 bacteria get in from a cultivated soil when this makes up the 



