SIGNIFICANCE OF COLON GROUP IN WATER 163 



Kaiser (1905) reports an interesting correlation between 



total numbers and B. coli in a series of 38 well waters. 



Of 1 1 wells containing over 200 bacteria per c.c. 90 per cent 



showed colon-like organisms in liter samples. Of 1 2 wells 



containing from 50 to 200 bacteria per c.c. 67 per cent 



gave colon-like organisms; of 26 wells with less than 50 



bacteria per c.c, only 27 per cent showed positive results. 



Fromme (1910) brings out the relation between B. 



coli and total numbers in 120 samples of well waters 



near Hamburg in the table below. 



RELATION BETWEEN TOTAL NUMBERS OF BACTERIA 

 AND B. COLI 



(Fromme, 19 10) 



Similar data obtained by one of us for some American 

 sources have been cited in Chapter I. Even Konrich 

 (19 10), who is exceedingly sceptical as to the value of 

 the colon test, has shown that an increase in the colon 

 content of the Jena water supply (a ground-water) 

 always followed a heavy rain which washed through 

 some of the colon bacilh in the soil. 



Colon Bacilli in Filtered Waters. One of the most 

 important appHcations of the colon test is in the control 

 of the operation of municipal water filters. It has 

 been used for this purpose for 10 years or more at 

 Lawrence, and Fuller laid stress upon its results in his 

 classic experiments on water purification in the Ohio 

 valley. At Cincinnati he records the presence of 



