EFFECT OF COPPER UPON WATER HACTERIA. 



59 



RESISTANCE OF VARIOUS BACTERIA. 



Several species of >)acteria oceuiriiio- coiuinoMly in Potomac River 

 water have been isolated, and comparative tests have ])een carried on 

 with these bacteria and with the colon bacillns. An examination of. 

 the tables showing- the exact results of these tests indicates clearly 

 that no dang-er to most of the common saprophytic bacteria can be 

 expected from using concentrations of copper sutticiently strong to 

 destroy Bacillus coli. To allow as little variation as possible in the 

 different tests all experiments were carried out in triple-distilled water. 

 This will probaldy explain the sensitiveness of most of the bacteria to 

 copper solutions, for, as (iildersleeve" has stated. '"The resistance of 

 bacteria washed in distilled water is lessened, due in all prol)al)ility to 

 the fact that some of the slimy substance which surrounds the bac- 

 terial cell and protects it to some extent from the action of detrimental 

 agencies is removed." For purposes of comparison the table showing 

 the action of copper sulfate on various ])acteria in tap water, pub- 

 lished by Gildersleeve,'' is reproduced ))elow. 



« Studies on the Bactericidal Action of Copper on Organisms in Water. 

 Journal of Medical Science, vol. 129, 1905, p. 754. 

 ''Op. cit., p. 759. 



100— VII 



American 



