CHAPTER LII 



BACTERIA IN WATER 



ALL natural waters contain a more or less abundant bacterial 

 flora. This fact, combined with our knowledge that the incitants of 

 several epidemic diseases and a number of minor ailments of a 

 diarrheal character are water borne, gives the bacteriological in- 

 vestigation of water a place of great importance in hygiene. In 

 nature, there are very few sources of water supply which do not 

 contain bacteria of one or another description. While pathogenic 

 bacteria are usually not present except in those waters which are 

 directly contaminated from human sources, a thorough understand- 

 ing of the quantitative and qualitative bacterial contents of all 

 natural waters is necessary in order that we may intelligently gather 

 comparative data as to the fitness of any given water for human 

 consumption. 



The gross appearance of water is rarely, if ever, an indication 

 of its danger. The turbid waters of running streams in sparsely 

 populated agricultural districts may be safe, while perfectly clear 

 well waters subjected to the dangers of contamination from neigh- 

 boring sinks or cess-pools may contain large numbers of pathogenic 

 germs. 



The diseases which are known to be more directly connected with 

 water supply are typhoid fever and cholera. 



Typhoid germs discharged from the bowel or from the urine of 

 typhoid patients or convalescents may be carried by the sewage or 

 from the neighboring soil into a river or lake and lead to infection 

 of the population deriving its drinking water from this source. 

 There are a great many investigations on record in which severe 

 typhoid epidemics have been traced to such sources. 



In the case of cholera, where the germs are discharged from the 

 bowels in enormous numbers, conveyance of the disease by water 

 is even more apparent, and the discoverers of the cholera germ 

 themselves, in their early work in Egypt and India, were able to 

 isolate the bacteria from contaminated water supplies. 



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