The Significance of B. Coli in Water. 123 



points of pollution he discovered a few colon colonies 

 upon his plates, not more than 4 to 6 per c.c. of the water. 

 He concluded that "the Bacterium coli, even when it is 

 added to a stream in great numbers, under certain circum- 

 stances disappears very rapidly, so that it can no longer 

 be detected in the examination of small portions of the 

 water." It should be noted that Hammerl's method 

 was much less delicate than the use of the dextrose tube 

 for preliminary incubation. 



The most important work upon the distribution of B. 

 coli has been that carried out in England by the bacteri- 

 ologists of the local government board, by Dr. Houston 

 in particular. This investigator (Houston, 1898; Houston, 

 i8g9 a ; Houston, i9oo a ) made an elaborate series of exam- 

 inations of soils from various sources to see whether the 

 microbes considered to be characteristic of sewage could 

 gain access to water from surface washings free from 

 human contamination. In the three papers published 

 on this subject the examination of 46 soils was recorded. 

 In only 10 of the samples was B. coli found, and of these 

 10, 9 were obviously polluted, being derived from sewage 

 fields, freshly manured land, or the mud-banks of sewage- 

 polluted rivers. The author finally concluded that "as a 

 matter of actual observation, the relative abundance of B. 

 coli in pure and impure substances is so amazingly dif- 

 ferent as to lead us to suspect that not only does B. coli 

 not flourish in nature under ordinary conditions, but that 

 it tends to even lose its vitality and die. " "In brief, I am 



