124 Elements of Water Bacteriology. 



strongly of opinion that the presence of B. coli in any num- 

 ber, whether in soil or in water, implies recent pollution of 

 animal sort. " Pakes (Pakes, 1900) stated on the strength 

 of an examination of "about 300 different samples of 

 water, " no particulars being publishedy that water from 

 a deep well should not contain B. coli at all, but that water 

 from other sources need not ^ be condemned unless the 

 organism was found in 20 c.c. or less. When colon bacilli 

 were found only in greater quantities than 100 c.c, the 

 water might be considered as probably safe. Horrocks 

 (Horrocks, 1901), after a general review of English prac- 

 tice, concluded that " when a water-supply has been , 

 recently polluted with sewage, even in a dilution of one in 

 one hundred thousand, it is quite easy to isolate the B. coli , 

 from I C.C. of the water." "I would say that a water 

 which contained B. coli so sparingly that 200 c.c. required 

 to be tested in order to find it had probably been polluted 

 with sewage, but the contamination was not of recent 

 date. " Chick (Chick, 1900) found 6100 colon bacilli per 

 c.c. in the Manchester ship canal, 55 to 190 in the pol- 

 luted River Severn, and numbers up to 65,000 per gram 

 in roadside mud. On the other hand, of 38 unpolluted 

 streams and rivulets, 31 gave np Bacillus coli and the 

 other 7 gave i per c.c. or less. The Liverpool tap water, 

 snow, rain, and hail showed no colon bacilli. 



One of the first elaborate applications of the colon test 

 was made by Jordan in the examination of the fate of 

 the Chicago sewage in the Desplaines and Illinois Rivers. 



