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 B. typhosus may live for weeks in river- 

 water, and that the longevity of B. jwodigiosu.s 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 B. typltosus 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 longevitv 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, 111., and for the purpose 

 of obtaining more reliable information, samples were also 

 taken from the tributarv streams. A glance at the diagram 

 (Fig. 3) will give an idea of the conditions. 



Fig. 3. 



