COLLOIDAL SOLUTIONS. 



Effect upon paratyphoid of exposure to colloidal solution of copper at room temperature. 



[Determination made in tubes of bouillon. + indicates growth after 48 hours' inoculation; indi- 

 cates no growth.] 



a Experiment conducted in test tubes containing 10 cc. each of sterilized water. The copper foil 

 was sterilized and added immediately before inoculating the tubes with the usual 3 mm. loop of a 

 24-hour culture of paratyphoid. 



Effect upon Microspira comma of colloidal solution of copper at various temperatures. a 

 [Determination made in Petri dishes.] 



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 M. comma. 



It is evident that the amount of surface exposed in any ordinary 

 copper tank would far exceed the amount demanded for the above 

 results, and it is likewise certain that after standing from 6 to 8 hours 

 at room temperature in a clean copper vessel water becomes safe to 

 drink even though it may have contained cholera and typhoid germs. 

 It remains to be seen whether or not the application of these facts to 

 conditions in the Tropics, where cholera is abundant, will be of any 

 value. It would seem that the . construction of canteens and other 

 water vessels from copper might serve as an additional safeguard, if 

 not an actual preventive of this disease, and would prove of consider- 

 able value where distillation or efficient filtration apparatus is not at 

 hand. 



