328 TYPHOID FEVER. 



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. 



