Quantitative Bacteriological Examination. 51 



miles below at Lockport, and numbers steadily decreasing 

 below to 3660 at Averyville, 159 miles below the point of 

 original pollution. Below Averyville 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 Donau 

 River above, and 110,000 at the mouth of, the Donau 

 canal. This number fell to 85,000 one kilometer below, 

 62,000 four kilometers below, and 40,000 seven kilometers 

 down the stream. Vincent (1905) records from 1000 to 

 46,000 bacteria per c.c. in the waters of more or less 

 polluted French rivers. Mayer (1902), on the other 

 side of the world, found 21 and 35 bacteria per c.c. in the 

 Shaho River, near its source, in the vicinity of the great 

 Chinese Wall, and from 100,000 to 600,000 in the highly 

 polluted Whangpo, near its mouth. 



In ground-waters we have seen that bacteria may occa- 

 sionally be present in considerable numbers, but, if so, they 

 are generally organisms of a peculiar character, incapable 

 of development on the ordinary nutrient media in the 

 standard time. Thus in forty-eight hours we often obtain 

 counts measured only in units or tens such as have been 

 recorded in Chapter I. When higher numbers are 

 present, the general character of the colonies must be 

 taken into account, since besides the slowly-growing 

 forms certain other water bacteria, which require a com- 

 paratively small amount of nutriment, may multiply at 

 times in a deep well or the basin of a spring. In such a 



