118 
IOWA ACADEMY OF SCIENCE 
that the principles involved in the purification which goes on in 
Burlington are typical in whole or in part of many other similar 
cases. Some bacteria perish almost immediately in the cold water 
of the lake; some settle to the bottom and perish there; some are 
killed by light as they float on the surface; some are devoured by 
predatory infusoria; the more hardy survive, perhaps, but do not 
multiply because of lack of food and other unfavoring conditions, 
and so are simply scattered by dilutiop; until finally only those 
remain which can permanently thrive in the now relatively pure 
water ; and these are apparently mostly harmless.” 
It has been shown that a rapidly flowing stream is not so injuri- 
ous to the bacteria as a stored body of water. It may be of 
interest in this connection also to call attention to the elimination 
of typhoid fever and intestinal bacteria in water coming from the 
Chicago Drainage Canal. In a report made by Drs. Jordan, Russell 
and Zeit it was shown that the typhoid organisms soon lost their 
vitality. “It may be concluded that the vast majority of the typhoid 
bacilli introduced into the sewage of the Chicago Drainage Canal, 
under the conditions which prevailed during the conduct of this 
experiment, disappear within two days after their introduction, and 
that while it may be true that individual cells endowed with special 
powers of resistance maintain their vitality for a longer period, 
the outcome of this experiment shows that such an assumption 
finds little warrant. Furthermore, assuming that such survival 
of typhoid bacilli with rare powers of resistance did sometimes 
occur, there is some ground for supposing that such adaptation to 
a saprophytic mode of life might be associated with a lowered viru- 
lence. The facts instanced by Hankin, and by Remlinger and 
Schneider, regarding the occasional presence of typhoid bacilli in 
natural waters apparently possessed of slight virulence, or even 
wholly innocuous, are sufficient to demand careful consideration of 
this possibility.” 
Since then, H. L. Russell and C. A. Fuller carried on investiga- 
tions of the longevity of the typhoid fever bacillus of natural waters 
and they arrived at the very important conclusion that these typhoid 
organisms lived somewhat longer. 
“Comparing these two types of surface waters, one from an in- 
land lake, of moderate dimensions, the other from a very much 
larger water reservoir, it appears that the results of these two sets 
of experiments are not greatly different. In Professor Zeit’s work, 
the average period of longevity was about seven days, while in our 
studies it has ranged from 8 to 10 days. Still, by far the most 
