EFFKCT OF COPl'KR UPON PATHOGENIC BACTERIA. 



35 



Kfict of <-(,pi>,r ttiiljilKil, iijxiii Micro><i)ir<i roni7)in at liifn-nil Innfirnitiirrft.a 

 [Deturniiiiatioii made iii I'etri dishcs.J 



" Kxpcrinifiits poiiduclrd in test lulics. cacli cniitainiiiK 5 v<\ nf sterilized water, portions of wliich 

 liad been previously treatt'd with the desired amounts of eoi)per sulphate. All tubes iiioeulaled 

 with a '.) nun. loop of a M-hour eidtureof .1/. nimiiid. 



Effect of copper sulphate upon MicroRpira comma at different temperatures.^ 



[Determinations made in Imilloii tubes. + indie itcs growth after 48 hours' incubation; — indicates 



no growth.] 



a Experiment conducted in test tubes each containing 5 cc. of sterilized water, part of which had 

 been previously treated with the desired amount of copper sulphate. All tubes inoculated with a 

 3 mm. loop of a IC-hour culture of .)/. cumnia. 



It will be seen that the concentration of copper required is consid- 

 erabl}" greater than the maximum necessary for the destruction of 

 alg-fe, and would, of course, be injurious to the aquatic animals nor- 

 mall}' present in a reservoir if it were allowed to act for any great 

 length of time. Experiments in this laboratory have demonstrated, 

 however, that the time necessai^ to remove Bacillus typhi is from 

 three to four hours in summer, twenty-four hours in the coldest 

 weather, and that under such conditions the solution does not injure fish 

 and frogs or the common aquatic plants such as Elodea^ MyriopJiyUum^ 

 and Lemna. To remove the copper at the desired time the method 



