60 



MISCELLANEOUS PAPERS. 



The figures in thi.s table are rather ^^urprising in connection with 

 the .statement that ''very little difference wa.s found between distilled 

 and filtered water used in the laboratory." The similarity here of the 

 action of copper in distilled and filtered tap water, contrasted with the 

 marked difference in the action of distilled and filtered tap water in 

 AYashington, emphasizes a point previously mentioned," that the water 

 itself deserves as careful a study as do the organisms contained therein. 

 This is suggested again in Phelps's^ report showing that with either 

 hard or turbid waters the germicidal efficiency of metallic copper is 

 much lessened. Again, in view of the high toxicity that investigators 

 have reported with copper in Philadelphia tap water, it seems neces- 

 sary to assume that this water either is peculiarly favorable to main- 

 taining the metal in a toxic state, or, what seems equally probable, 

 for rendering the bacteria unusually sensitive. 



The results of our own experiments are given in the following tables. 

 All the experiments, unless otherwise indicated, were conducted in 

 Weber resistance glass test tubes, each containing 10 c. c. of water 

 triple distilled from glass, portions of which had been treated pre- 

 viously with the desired amount of copper sulfate. All tubes were 

 inoculated with a 2 mm. loop of the proper organism. The temper- 

 ature during each experiment varied from 18^ to 22^ C. 



Table I. — Effect of copper sulfate upon Bacillus mycoides. 



Table II. — Effect of copper sulfate upon Bacillus megatherium. 



c Bui. 76, Bureau of Plant Industry, U. S. Dept. of Agriculture, p. 12; and Keller- 

 man, Journal New England Water Works Association, vol. 19, 1905, p. 536. 

 ^ .Tournal New England Water Works Association, vol. 19, 1905, pp. 537-589. 



100— VII 



