BACILLUS TY PHOSUS. 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. 
