16 ELEMENTS OF WATER BACTERIOLOGY 



Freudenreich (Freudenreich, 1888) have shown that an 

 " antagonism " exists when bacteria are grown in 

 artificial culture media, such that the substratum which 

 has supported the growth of one form may be rendered 

 antiseptic to another. Frost (1904) has exhaustively 

 studied the phenomenon of antagonism by exposing 

 typhoid bacilli in collodion sacs to the action of certain 

 soil and water bacteria growing in broth. Artificial 

 culture media, however, offer conditions for bacterial 

 development which are scarcely paralleled in natural 

 waters. It is difficult to beHeve that under ordinary 

 conditions poisons are produced of such power as to 

 render a stream or lake specifically toxic for any par- 

 ticular type of bacteria. It does appear indeed from 

 the experiments of Jordan, Russell and Zeit (1904), and 

 Russell and Fuller (1906), which will shortly be referred 

 to more fully, that the life of typhoid germs is shorter 

 in water containing large numbers of other bacteria 

 than in that of greater purity. Horrocks (1899), too, 

 found freshly isolated typhoid bacilli alive in sterile 

 sewage after 60 days; while they disappeared in 5 days 

 when B. coli was also present. These phenomena may 

 be due, however, to a struggle for oxygen, or for food, 

 rather than to the assumed presence of highly toxic 

 bacterial products, of which there is no independent 

 evidence. 



Many investigations conducted since the pioneer 

 researches of Downes and Blunt (Downes and Blunt, 

 1877) have confirmed the results reported by them, 

 which showed that direct sunlight is fatal to most 

 bacteria in the vegetative state and even to spores if 



