CHAPTER LIII 

 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 char- 

 acter are water borne, gives the bacteriological investigation 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 understanding of the quantitative and qualitative bacterial 

 contents of all natural waters is necessary in order that we may in- 

 telligently 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 neighboring 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. 



In regard to the less clearly understood diarrheal diseases, dysen- 

 tery, cholera infaiitum, etc., the direct relation to water supply has not 



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