92 ELEMENTS OF WATER BACTERIOLOGY 



same authors (Stokes and Hachtel, 1912) have more 

 recently reported the isolation of the typhoid bacillus 

 from the water in the neighborhood of a polluted 

 oyster bed. 



The search for the typhoid bacillus is usually sug- 

 gested when an outbreak of the disease has cast strong 

 suspicion upon some definite source of water-supply. 

 By the time an epidemic manifests itself, however, 

 the period of the original infection is long past, and the 

 chances are good that any of the specific bacilli once 

 present will have disappeared. While elaborate exper- 

 iments have shown that B. typhi may persist in 

 sterilized water for upwards of 2 months and in unster- 

 ilized water from 3 days to several weeks, the number 

 of the organisms present is always very rapidly reduced. 

 Even in highly polluted water their number is propor- 

 tionately small; as is well shown by the experiments 

 of Laws and Andrewes (Laws and Andrewes, 1894) 

 who entirely failed to isolate the typhoid bacillus from 

 the sewage of London and found only two colonies of 

 the organism on a long series of plates made from the 

 sewage of a hospital containing forty typhoid patients. 

 So Wathelet (Wathelet,i895) found that of 600 colonies 

 isolated from typhoid stools and having the appearance 

 characteristic of B. coli and B. typhi only 10 belonged 

 to the latter species. 



Epidemiological evidence confirms these results and 

 indicates that the number of typhoid bacilli even in 

 polluted water probably is never very great, while the 

 fate of Lowell and Lawrence in 1890-91 and the more 

 recent epidemics at Butler, Pa., and Ithaca, N. Y., 



