BACTERIA IN WATER 193 



particle of organic matter, possibly feces, is swallowed. 

 This may contain many thousand organisms. 



Although cholera organisms live in water a shorter 

 time than typhoid bacilli, they are said to be viable 

 for several weeks. Relatively more cholera organisms 

 are discharged with a cholera stool than is the case of 

 typhoid bacilli in enteric fever. Dysentery bacilli live 

 only a short time in water probably, and the impor- 

 tance of water in the dissemination of dysentery is ques- 

 tioned by some observers. Certain it is that some 

 epidemics appear to be water-borne. 



Typhoid and colon bacilli are always present in 

 typhoid stools. It is hardly probable that the former 

 could get into water without the other. Moreover, 

 the colon bacillus is present in all alimentary tracts. 

 It is more easily detected in any mixture or solution 

 than any other of the intestinal bacteria. Therefore it 

 is taken as an indication of sewage pollution in water. 

 This may not mean that typhoid bacilli are present, but 

 merely that contamination of water by sewage from 

 animal sources has occurred. Whether from man or 

 animals, it is obvious that dejecta should not come into 

 water intended for human consumption. The methods 

 of water examination now in use all aim at the detec- 

 tion of Bacillus coll. Because of its peculiarities in the 

 fermentation of sugars, certain media are adopted as 

 standards for its isolation. Water is carefully collected 

 and kept upon ice so that no increase of bacteria will 

 occur. In the laboratory suitable measures are taken 

 to determine the whole number of bacteria and the 

 presence of the colon bacillus. The whole number is 

 estimated by growing the water in flat plates of agar 

 13 



