110 BACTERIOLOGY FOR NURSES 



to distinguish B. typhosus from the allied organisms 

 which SO closely resemble it. 



While the bacillus of typhoid is frequently found in 

 soil and in water, its presence can always be traced 

 to the discharge of excreta from typhoid fever 

 patients; the origin is often remote and obscure, but 

 careful investigation invariably establishes the fact 

 that such pollution of soil and water always arises 

 from the excreta of typhoid-fever patients. 



It was formerly thought that the bacillus of ty- 

 phoid was capable of reproduction in both soil and 

 water, but this is now acknowledged to be wrong, 

 experiments showing that, while the bacillus may 

 survive in sterile water for three months and in ordi- 

 nary streams for five or six days, it does not multiply 

 in either case. 



In the soil or in privy vaults, the bacilli may sur- 

 vive for months, and may then be washed into 

 streams by heavy rains, or they may infect the soil 

 when the contents of the vault is used for fertilizing 

 purposes, but they do not multiply in the soil. 



Typhoid Infection in Animals. — Repeated experi- 

 ments have failed to produce the typical typhoid 

 fever of the human being in animals, although infec- 

 tions have occasionally occurred. 



Prevalence of Typhoid Fever. — Typhoid fever is 



