The Bacteria in Natural Waters. 15 



canal water may be attached to gross particles, as 

 evidenced by their sedimentation in a few hours. 

 Jordan (Jordan, 1900) is firmly of the opinion that in the 

 lower part of the Illinois River, where there is a fall of 

 but 30 feet in 225 miles, the influences summed up by the 

 term sedimentation are sufficiently powerful to obviate 

 the necessity for summoning another cause "to explain 

 the diminution in numbers of bacteria," and he further 

 adds: "It is noteworthy that all the instances recorded 

 in the literature where a marked bacterial purification 

 has been observed, are precisely those where the conditions 

 have been most favorable for sedimentation." 



Little is known as to the share of other organisms in 

 hastening the decrease of bacteria in stored water. 

 Doubtless predatory Protozoa play some part in the 

 process. Huntemuller (1905), after infecting water 

 containing Protozoa with typhoid bacilli, found the 

 Protozoa crowded with bacteria; and he observed under 

 the microscope the actual ingestion of the living and 

 motile bacilli. Korschun (1907) and others have ob- 

 tained similar results and consider the activity of Protozoa 

 to be an important factor in self-purification. 



Fehrs (1906) found that typhoid bacilli would live 

 for 7 days in unsterilized Gottingen tap water, for 46 

 days in the same water sterilized, and for 13 days in water 

 inoculated with a culture of flagellate Protozoa after 

 sterilization. Water bacteria were of course added 

 with the Protozoa. 



