QUANTITATIVE BACTEEIOLOGICAL ANALYSIS 55 



ground is a possible source of danger. The excess of 

 bacteria in surface-waters during the spring and winter 

 months is by no means an exception to the general 

 rule that high numbers are significant, since the peril 

 from supplies of this character is clearly shown by the 

 spring epidemics of tj-phoid fever which at the times of 

 melting snow visit conmiunities making use of impro- 

 tected surface-waters. Streams receiving direct con- 

 tributions of sewage exhibit a similar excess of bacteria 

 at all times, numbers rising to an extraordinary^' height 

 near the point of pollution and falling off below as the 

 stream suffers dilution and the sewage organisms jjerish. 

 Miquel (Miquel, 1886) records 300 bacteria per c.c. 

 in the water of the Seine at Choisy, above Paris; 1200 

 at Bercy in the vicinity of the city, and 200,000 at St. 

 Denis after the entrance of the drainage of Paris. 

 Prausnitz (Prausnitz, 1890) found 531 bacteria per c.c. 

 in the Isar above Munich, 227,369 near the entrance of 

 the principal sewer, 91 11 at a place 13 kilometers 

 below the city, and 2378 at Freising, 20 kilometers 

 further down. Jordan Qordan, 1900), in his study 

 of the fate of the sewage of Chicago, found 1,245,000 

 bacteria per c.c. in the drainage canal at Bridgeport, 

 650,000 at Lockport, 29 miles below, and numbers 

 steadily decreasing to 3660 at Averyville, 159 miles 

 below the point of original pollution. Below Avery- 

 ville the sewage of Peoria enters and the numbers 

 rise to 758,000 at Wesley City, decreasing to 4800 in 

 123 miles flow to Kampsville. Brezina (1906) found 

 1900 bacteria per c.c. in the Danube River above, and 

 110,000 at the north of the Danube canal. This number 



