196 



MICROBIOLOGY OF WATER AND SEWAGE. 



B. Typhosus (page 640). Very few instances are recorded in bac- 

 teriological literature of the direct isolation of the typhoid bacillus from 

 infected water. The organism is not long-lived, even in pure water 

 (eight to ten days) ; and when exposed to the action of sewage bacteria, 

 its longevity is greatly diminished (not more than five to six days). A 

 few resistant specimens may remain alive for longer periods of time. 



Although the typhoid bacillus has been found so infrequently in 

 water, it is well understood at the present time that the purification of 

 the water supply of a town or city produces a marked decrease in the 

 number of cases and in the mortality from typhoid fever, as the following 

 table shows: (See also Fig. 57.) 



Deaths from Typhoid Fever per 100,000 per Year. 



Not only has such a marked improvement followed the purification of 

 public water supplies in the case of typhoid fever, but it has been shown 

 by statistics that "where one death from typhoid fever has been avoided 

 by the use of better water, a certain number of deaths, probably two or 

 three, from other causes have been avoided." 



In the routine examination of water, no particular effort is made to 

 isolate this organism, owing to the difficulty of the task. The tests that 

 the present day investigator has to satisfy are extremely thorough; and 

 unless the suspected organism conforms to the whole of these necessary 

 tests it cannot be accepted as true B. typhosus. 



Msp. Comma (page 645). The spirillum, or vibrio, of Asiatic cholera 

 is an intestinal organism; and the disease it produces is spread largely 

 by water. Epidemics of cholera are more easily traced to their source 



