54 ELEMENTS OF WATER BACTERIOLOGY. 



Rellingen in 1901. In these cases the water was directly 

 plated upon Eisner's medium or phenolated gelatin with 

 no preliminary process of enrichment. 



The search for the typhoid bacillus is usually suggested 

 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 dis- 

 appeared. While elaborate experiments have shown 

 that B. typhi may persist in sterilized water for upwards 

 of two months and in unsterilized water from three days 

 to several weeks, the number of the organisms present is 

 always very rapidly reduced (Frankland, 1894). Epi- 

 demiological evidence confirms the results of Laws and 

 Andrewes which teach 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 seems strongly 

 to demonstrate that even a small number of virulent 

 organisms can bring about an almost wholesale infection. 

 Indeed if the virulent organism were as abundant as some 

 recent results would indicate (Remlinger and Schneider, 

 1897), the human race would long since have been exter- 

 minated. On the whole it seems that since a positive 

 result is always open to serious doubt, and a negative 

 result signifies nothing, the search for the typhoid bacillus 

 itself, however desirable theoretically, cannot be regarded 

 at present as generally profitable. 



The isolation of the cholera bacillus from water can 



