1 24 EDWARDS. 



represents the proportion of samples at first rejected, but in some cases 

 later investigation made with great precautions forced the conclusion 

 that the samples were condemned in the first place because of contamina- 

 tion in securing the specimen. 



Wells and cisterns showed 63.3 per cent of rejections and I do not 

 doubt but that this number is far too low, for in instances the request for 

 examination did not specify whether the sample was from an ordinary or 

 an artesian well. 



The miscellaneous places mentioned in the table include rivers, esteros, 

 rice paddies, ponds, pools, ditches and tanks. Many of the requests for 

 examination of samples called for only a partial examination for the 

 presence of the cholera organism, and this accounts for the low per- 

 centage condemned. 



AVater should be condemned («) for the presence of animal parasites, 

 (b) for the presence of pathogenic bacteria, (c) when the count is above 

 200 bacteria per cubic centimeter. 



The specimens of distilled water condemned were almost without 

 exception rejected because of the presence of protozoa. It would, 

 therefore, be legitimate to conclude that, in the handling of water, there 

 is almost as much danger of contamination with protozoa as there 

 is with bacteria and possibly this contamination is accompanied by greater 

 danger to those who use the water for drinking jmrposes than the other. 

 It is therefore advisable, in order to insure safety of drinking water, to 

 make as few transfers from one receptacle to another as is possible after 

 sterilization. I have already mentioned the good condition of reliable 

 brands of water bottled and for sale, but can not condemn too strongly 

 the handling which is ordinarily given to distilled and other potable 

 waters when secured in large quantities. 



A study of the above reports causes me to advocate a triple biological 

 examination of all samples of water as follows : 



Twenty- five cubic centimeters of a 10 per cent peptone solution are added to 

 about 225 cubic centimeters of water in a sterile flask (about the amount probably 

 drunk by an individual at one time). The growth should be examined after 

 twenty-four, forty-eight and seventy-two hours, with due precaution against 

 contamination upon opening for the first two examinations. The report should 

 mention amcebie, flagellata and ciliata. 



Two cubic centimeters should be withdrawn witli a sterile syringe at the 

 24-hour examination and injected into the peritoneal cavity of a guinea pig or 

 rabbit; if the animal does not die within forty-eight hours it is quite probable 

 that there are no pathogenic bacteria present. Plates should be made from the 

 original peptone culture, containing 1, 0.1, 0.01 and 0.001 cubic centimeter of 

 suspected water, respectively, and placed in the incubator for forty-eight hours 

 before the colony count is made. 



The figures appearing in this paper bring me to the conclusion that 

 tap water, cistern water, ordinary well water, and water only filtered as 

 a means of sterilization should not be used for drinking purposes in the 





