25 



In view of the general scientific interest awakened as to the 

 use of sulphate of copper in high dilutions as a purifier of water 

 reservoirs, following G. T. Moore's bulletin ^ on that subject, a 

 special series of experiments was undertaken with high dilutions of 

 sulphate of copper on various suspensions of amoebae. The 

 importance of the subject in connection with the amoeba-infected 

 water supply of Manila is very apparent and was long since recog- 

 nized by the Board of Health for the Philippine Islands. In com- 

 pliance with a request from Maj. E. C. Carter, Commissioner of 

 Public Health, I reported the results of my experiments with high 

 dilutions of copper sulphate to Dr. E. P. Strong, the Director of 

 the Biological Laboratory, under date of January 30, 1905. The 

 results are in part as folloAvs: After an application of a solution 

 of cupric sulphate 1-5,000 for one hour, many amoebae and a few 

 spirilla grew on the transplants; after 1-10,000 for two hours, 

 many amoebae and a few spirilla grew; after 1-100,000 for forty- 

 eight hours, many amcebae and a few spirilla grew. At a later date 

 the above test was repeated under practically the same conditions, 

 except that control transplants were made to cholera plates, and 

 both the amoebas and the spirilla grew equally well after exposure 

 for forty-eight hours to copper solutions 1-100,000 and 1-200,000. 



All the tests mentioned thus far were conducted with amoeba 

 suspensions of 8 cubic centimeters of fluid to one forty-eight-hour 

 slant agar culture of amoeba and spirilla. Another set of tests was 

 carried out to compare the effects of the copper solutions on amoebae 

 suspensions of varying concentration. At the same time controls 

 of the suspensions of amoebae were made, using precisely the same 

 dilutions as those treated with copper and making transplants from 

 these controls and the suspensions treated with copper, at periods 

 varying from twenty-four to ninety-six hours. It was thus possible 

 to determine by comparison to what extent the destruction or atten- 

 uation of amffiba suspensions might be due to an unfavorable me- 

 dium, diminished nourishment, etc. The following were results 

 obtained ])y treating for ninety-six hours three different concentra- 

 tions of amoeba suspensions with copper sulphate 1-100,000 : 



Eight-cubic centimeter suspension : Transplants developed rich 

 growth of amoebae and fair growth of spirilla. 



^Bulletin Xo. G.'i, Bureau of Plant Industry, U. 8. Dept. of Agriculture. 



