290 Trans. Acad. Sci. of St. Louis. 
it was shown that in sterilized strong or dilute sewage B. 
typhosus was found alive after 60 days, but that in unsterilized 
sewage there was no evidence that this organism lived longer 
than 14 days. Dr. Ravold and others have also shown ex- 
perimentally that &. typhosus may live for weeks in river- 
water, and that the longevity of B. prodigiosus under similar 
conditions is much the same. We see from this, that if it is 
possible for B. prodigiosus to be carried for many miles by 
means of a stream and to be detected in a water-supply, it is 
probable that BL. typhosus under the same conditions would 
also be conveyed over considerable distances, and that a water- 
supply might then easily become contaminated. However, 
in arriving at positive conclusions in regard to the presence 
and the effect of disease germs in drinking-water, there are 
many factors to be considered, and, under the given and 
natural conditions, it is of the greatest importance to have 
definite information on the longevity of disease organisms 
occurring in water and in sewage. 
It would be interesting in this connection to note the 
diminution in the number of bacteria in a running body 
of water heavily charged with sewage. In 1901, during 
a period of two months, I had excellent opportunity of 
making observations of the character of the water of the 
Drainage Canal at and near Joliet, Ill., and for the purpose 
of obtaining more reliable information, samples were also 
taken from the tributary streams. A glance at the diagram 
(Fig. 3) will give an idea of the conditions. 
