152 ELEMENTS OF WATER BACTERIOLOGY 



failed to find colon bacilli in the river by this method, 

 except immediately below the various towns situated 

 upon it; at these 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 circumstances disappears 

 very rapidly, so that it can no longer be detected in 

 the examination of small portions of the water." 



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; Hous- 

 ton, 1899*; Houston, 1900^) made an elaborate series 

 of examinations of soils from various sources to see 

 whether the microbes considered to be characteristic 

 of sewage could gain access to water from surface wash- 

 ings 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 observa- 

 tion the relative abundance of B. coli in pure and impure 

 substances is so amazingly different 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 vitaUty and die." " In brief, I am strongly 

 of opinion that the presence of B. coli in any number, 

 whether in soil or in water, implies recent pollution of 



