118 Drinking- Water and some of its Impurities. 



taken into the system, which in about a year developes 

 into a white worm that passes through the body and makes 

 its appearance usually in one of the legs. The part 

 aflected begins to swell, and the native physicians to 

 whom the symptoms are well known immediately make 

 an incision, and dextrously catching hold of the worm, 

 slowly wind it off on a stick. This is an operation which 

 has to be done with great care, as should the worm be 

 broken each part would become a separate worm, and 

 would be the cause of innumerable ulcers. There are 

 often many such worms at the same time. The disease is 

 accompanied by severe pains in the bones and internal 

 heat and thirst. ^ ^ ^ ^ Most of the water for 

 drinking is taken from the large pools and tanks where it 

 has remained in a stagnant state for many months." * * 

 "When sewage flows into running streams, besides being 

 largely diluted, a portion of it is oxidized and another por- 

 tion is taken up by fish, infusoria, aquatic plants, etc. 

 The completeness of this oxidation is still a disputed point 

 with chemists, some holding that the water is completely 

 purified by merely flowing ten or twelve miles, especially 

 if it be broken up by dams or rifts, and others contending 

 that it can never be completely purified in this manner. 

 The Thames, which receives a large amount of sewage 

 above London, is, according to the report of the committee 

 of chemists appointed by the royal commission, " perfectly 

 wholesome, palatable and safe " at that city. It is claimed 

 on the other side, that water need not necessarily contain 

 enough animal matter to be readily recognized by chemical 

 tests in order to be prejudicial to health. " At the present 

 time, a chemical analysis alone is not sufficient to deter- 

 mine the desirability of a given water supply. The rice- 

 water evacuations of a cholera patient, diluted with no very 

 large amount of water, would form a liquid in which 

 chemical tests would fail to indicate the presence of any- 



