352 TYPHOID FEVER. 



any particular organism isolated is identified as the one or 

 the other ; probably there are saprophytes existing in nature 

 which only differ from them in one or two reactions. In 

 the examination of water, the addition of .2 per cent 

 carbolic acid to the medium inhibits to a certain extent 

 the growth of other bacteria, while the B. typhosus and the 

 B. coli are unaffected. In examining waters, the ordinary 

 plate methods are generally used. Klein, however, filters 

 a large quantity through a Berkefeld filter and, brushing 

 off the bacteria retained on the porcelain, makes cultures. 

 A much greater concentration of the bacteria is thus 

 obtained. 



