SIGNIFICANCE OF COLON GROUP IN WATER 173 



water as far as bacteriology can prove it. That when 

 present, its numbers form a reasonably close index of 

 the amount of pollution, the authors above quoted have 

 proved beyond reasonable cavil. It may safely be 

 said that when the colon bacillus is found in such abun- 

 dance as to be isolated in a large proportion of cases 

 from I c.c. of water, itjs generally proof of the presence 

 of serious pollution. 



The standard here suggested is much more lenient 

 than the one set forth by the U. S. Treasury Depart- 

 ment for drinking water supplied to the public by com- 

 mon carriers (see p. i39</)- Instead of permitting some 

 20 or 40 colon bacilli for each 100 c.c. of water as the 

 ordinary test of five i-c.c. samples does, the Treasury 

 Department condemns a water containing over 2 colon 

 bacilli in 100 c.c. It must be remembered, however, 

 that this government standard was " recommended 

 only for application to the special case in question"; 

 and the Commission pointed out that, with water 

 served on trains, it was necessary to set " narrower 

 limits for permissible impurities of definitely dangerous 

 character " than would be the case with waters where 

 a sanitar>^ inspection of the source could be made. i 



Mr. George W. Fuller and his colleagues, in testify- 

 ing before the International Joint Commission on the 

 Pollution of Boundary Waters, recommended a stand- 

 ard for raw waters before filtration of 500 B. coli per 

 100 c.c. of water expressed as an annual average and 

 determined from a considerable number of confirmatory 

 tests made throughout the year. 



