BA CTERIOLOGIGA L STUD T OF WA TER. 487 



posed to be concerned in the production of disease, partic- 

 ularly typhoid fever, either in isolated cases or in wide- 

 spread epidemic outbreaks, and almost as often do 

 reliable bacteriologists fail to detect the bacillus that is 

 the cause of typhoid fever in these waters. 



The failure to find the organisms of typhoid fever in 

 water by the usual methods of analysis does not by 

 any means prove that they are not present or have not 

 been present. The means that are ordinarily employed 

 in the work admit of such very small volume of water 

 being used in the test that we can readily understand 

 how these organisms might be present in moderate num- 

 bers and yet none of them be included in the drop or 

 two of the water that are taken for study. The con- 

 ditions are not those of a solvHorij each drop of which 

 contains exactly as much of the dissolved material as 

 do all other drops of equal volume, but are rather those 

 of a suspension in each drop or volume of which the 

 number of swtpended particles is liable to the greatest 

 degree of variation. Furthermore, there are other rea- 

 sons that would, a priori, preclude our expecting to find 

 the typhoid bacilli in water in which we may have rea- 

 son to believe they had been deposited, viz., attention 

 is not usually directed to the water until the presence of 

 the disease has become conspicuous, usually in from 

 three to four weeks after the time when the pollution 

 probably occurred. Three or four weeks are ordinarily 

 sufficient time for the delicate, non-resistant bacillus of 

 typhoid fever to succumb to the unfavorable conditions 

 under which it finds itself in water. By unfavorable 

 conditions are meant the absence of suitable nutrition; 

 unfavorable temperature; probably the antagonistic in- 

 fluence of more hardy saprophytic bacteria, particu- 



