BACILLUS TYPHOSUS. 443 



The Detection of Typhoid Bacilli in Water. This sub- 

 ject is considered on pages 247 and 248. There is 

 absolutely no doubt that the contamination of streams 

 and reservoirs is the frequent cause of the outbreak of 

 epidemics of typhoid fever, but the actual finding and 

 isolation of the bacilli is a very rare occurrence. This 

 is owing to the contamination often having occurred 

 and passed away before the bacteriological examination 

 is undertaken, and also because of the great difficulties 

 met with in detecting a few typhoid bacilli when they 

 are associated with large numbers of other bacteria. 

 The greater the amount of contamination which is 

 thrown into the water, and the shorter the time which 

 elapses between the infection and the drinking of the 

 water, the greater is the danger. 



The typhoid bacillus and the colon bacillus of 

 Escherich resemble each other in many respects. The 

 characteristics of each, which allow us to differentiate 

 the one from the other, will be considered at the end of 

 the description of the colon bacillus. 



