60 KRAEMER— ACTION OF COPPER FOIL [April 13, 



It is seen from the foregoing table that while we began with 

 approximately 5,000 organisms of colon bacilli to the cubic centi- 

 meter in the case of the tap water, there were over 700,000 at the 

 end of sixty days ; and that in the case of the stone filtered water 

 where the initial number of organisms was about 10,000 they in- 

 creased on an average similar to those in the tap water. In the 

 case of the water from the Berkefeld filter, however, beginning with 

 10,000 organisms to the cubic centimeter, there was a rapid 

 diminution of the organisms, so that but about 2,500, or about 25 

 per cent, of the organisms persisted at the end of six hours, and 

 while they continued to multiply after this still the number was 

 considerably less than in either the tap water or stone filtered water, 

 showing that with Berkefeld filtered water there is some agency 

 which inhibits the growth of the colon bacilli. This we concluded 

 to be due to the copper dissolved from the spigot to which the 

 filter was attached, as already suggested. 



In the experiments with the typhoid organisms it was found that 

 they multiplied in number in both the tap water and stone filtered 

 water persisting for fourteen days, after which they disappeared, as 

 was also the case in some other experiments ; but in the case of 

 Berkefeld filtered water they entirely disappeared within four hours, 

 which was also the case in three other experiments not here re- 

 corded. It may also be stated that it was not unusual to observe in 

 the case of both tap and stone-filtered water, where cultures of the 

 typhoid bacillus were used, that if the organisms persisted until the 

 fourteenth day, they would multiply enormously after that as shown 

 for tap water and distilled water in Table II. 



In an investigation of this kind many lines of experiment are 

 suggested, and it was thought desirable to carry on another series 

 of experiments with a view of testing the toxicity of solutions in 

 which metallic copper had been allowed to remain for varying 

 lengths of time. In these experiments sterilized distilled water 

 and stone filtered water were used. To 600 cc. of water in a 

 graduate 8 strips of copper foil 15 x 130 mm. were added. The 

 graduate was agitated continuously and 100 cc. of the solution 

 were removed at the end of 1, 5, 10, 20 and 30 minutes. The 

 respective solutions were placed in Erlenmeyer flasks and sterilized 

 in an autoclave at no°C. for 30 minutes. To these were added 

 18- to 24-hour cultures of typhoid bacilli, and plates made with 

 results as indicated in the two following tables : 



