384 CHAMBERLAIN AND VEDDER. 



any water from entering the sterilizer if the current is interrupted. 

 The apparatus is small and one type is portable. The water is neither 

 heated nor altered in taste by the process. It provides a rapid method 

 by which a badly polluted water may be transformed into one of potable 

 quality, and finally it is very economical in operation. The low cost 

 should place it within the means even of poor native villages, a small 

 gasoline engine being capable of producing sufficient power. 



For army use this apparatus with dynamo and gasoline engine could 

 be readily carried in an escort wagon or automobile. In case the latter 

 were used a special gasoline engine could be dispensed with, and the 

 motor of the automobile utilized to drive' the dynamo. The small type 

 of apparatus delivers 130 gallons (530 liters) of sterile water per hour, 

 and it would be capable of supplying an entire regiment with a quart of 

 water for each man after only three hours' operation. The larger appa- 

 ratus, although designed for permanent installation, could also be carried 

 in an escort wagon, and would supply 133,000 gallons (538,000 liters) 

 in twenty-four hours, thus providing in twelve hours a little over 3 

 gallons (13 liters) of sterile water for every soldier in a division of 

 30,000 men. The delivery of pure water would commence within a few 

 minutes after arrival in camp, would be continuous, and the water would 

 be unchanged in taste, a great desideratum when dealing with soldiers 

 whose objection to the fiat taste of boiled water is well known. Also 

 there would be no time wasted in waiting for water to cool as is the case 

 when sterilization by heat is resorted to. 



But in considering the use of such a sterilizer in the Tropics we 

 are confronted by the fact that bacterial pollution is not the only nor, 

 in some cases, the most important danger that lurks in the drinking 

 supply. Amoebae are found in practically all tropical surface waters, 

 and while the free-living species are not pathogenic, it is to be expected 

 that Entamoeba histolytica will be encountered under the same conditions 

 of pollution that would cause the presence of typhoid bacilli or cholera 

 spirilla in the water. In similar circumstances, Balantidium coli, Lam- 

 hlia intestinalis , and other protozoa, as well as the ova or larvae of various 

 parasites are liable to occur. Therefore it is important, before adopting 

 any method of water purification for tropical countries, to show that the 

 procedure will protect the consumers against infections with animal 

 parasites as well as against the bacterial causes of disease. Filter beds 

 will eliminate 99 per cent of the bacteria in water, but will not remove 

 amoebae or other protozoa, so that this method of water purification is 

 impracticable in the Philippines for this reason and also because of its 

 great expense. 



It seems quite probable, from what we know of the action of the 



