EFFECT OF COPPER UPON PATHOGENIC BACTERIA. 



35 



Effect of copper sulphate upon Microspira comma at different temperatures. <* 



v 



[Determination made in Petri dishes.] 



a Experiments conducted in test tubes, each containing 5 cc. of sterilized water, portions of which 

 had been previously treated with the desired amounts of copper sulphate. All tubes inoculated 

 with a 3 mm. loop of a 14-hour culture of Jf. comma. 



Effect of copper sulphate upon Microspira comma at different temperatures.* 1 



[Determinations made in bullion tubes. + indicates 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 16-hour culture of M. comma. 



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

 erably greater than the maximum necessary for the destruction of 

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

 mally 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 necessary to remove Bacillus typhi is from 

 three to four hours in summer, twent}'-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, Myriophyllum, 

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



