180 MIOEO-ORGANISMS IN WATER 



on July 17 by the appearance of typhoid bacilU in the 

 filtrate. This result clearly indicates that even the pol- 

 luted canal-ioater did not in itself contain the necessary 

 fahuluiin for the typhoid hacilli to grow through the filter - 

 pores^ and that this was only rendered possible after the 

 addition of the bouillon. 



From another filter ^ fed with typhoid germs, the fil- 

 trate was sterile to start with ; on the following day 

 5 c.c. of sterile bouillon were added, and two days later 

 typhoid bacilli appeared in the filtrate ; but they gra- 

 dually decreased in numbers, although fresh typhoid 

 organisms were twice introduced into the unfiltered 

 water. After an interval of seven days 5 c.c. of bouil- 

 lon were again added to the water, and the number of 

 typhoid organisms in the filtrate rose on the following 

 day from 9 to 6,139 per c.c. without any fresh infec- 

 tion having been made. The large increase was due to 

 the rapid multiplication of the few isolated typhoid 

 bacilli remaining in the pores of the filter, in conse- 

 quence of the supply of food material in the shape of 

 bouillon. 



Schofer is of opinion that typhoid bacilli, as ordi- 

 narily present in water, are not supplied with the re- 

 quisite conditions for their growth and multiplication, 

 and are, therefore, incapable of growing through these 

 filters and reaching the filtrate ; these conditions are, 

 however, furnished when a sufficient supply of food 

 material is contained in or added to the liquid to be 

 filtered, in which case the cylinders are no longer able 

 to retain the typhoid bacilli. These experiments ex- 

 plain the unsatisfactory results obtained by Kirchner 

 in his investigations referred to above, and at the same 

 time indicate the nature of the precautions which should 



^ The pure water (Hochquellwasser) of the Vienna supply was used, 

 and no previous deposit of organic material was secured. 



