8o Elements of Water Bacteriology. 



should be received with caution. Since the introduction 

 of the Widal (Widal, 1896) reaction, founded on the 

 fact that typhoid bacilli examined under the microscope 

 in the diluted blood-serum of a typhoid patient lose their 

 motility and "agglutinate" or clump together, an impor- 

 tant aid has been furnished in the diagnosis. Yet serum 

 tests are notably erratic, and insufficient to identify an 

 organism without an exhaustive study of biochemical 

 reactions. Many organisms are agglutinated by typhoid 

 serum in a more or less dilute solution, and agglutina- 

 tion tests are not significant unless obtained in dilutions 

 as great as 1-500 or i-iooo. The discovery of the 

 Bacillus dysenteriae of Shiga,' which closely resembles 

 the typhoid bacillus, has made the identification of the 

 latter more dubious than ever. Hiss (1904) has shown 

 that the fermentation and agglutination reactions of the 

 two organisms are in many respects alike, and Park and 

 his associates (1904) have shown that there are not less 

 than three distinct types of dysentery bacilli forming that 

 group. 



In the work so far described the typhoid organism was 

 not isolated from polluted water, but from artificial 

 mixtures or excreta.- There are, however, a number of 

 cases in which the organism has imdoubtedly been iso- 

 lated from polluted water, as by Kiibler and Neufeld 

 (Kiibler and Neufeld, 1899), who examined a farmhouse 



' For an account of the Biology of B. dysenterias the student is 

 referred to an article by Dombrowsky, 1903. 



