The Significance of B. Coli in Water. 13 1 



in I C.C.; 97 samples gave negative results in 10 cc; 45 in 

 100 cc, and 4 had 20 B. coli even in 1000 cc 



B. COLI IN THE RIVER THAMES AT VARIOUS POINTS. 

 (HOUSTON, igo4^.) 

 Percentage of positive results. 



With ground-waters the story is the same. Even in 

 sources of excellent quality we should expect to find, and 

 we do sometimes find, colon baciUi in large volumes of 

 water. Abba, Orlandi, and Rondelli (1899) showed by 

 experiments with B. prodigiosus at Turin that when 

 bacteria are present in great numbers on the surface of the 

 ground, a few may penetrate for a considerable distance 

 and ultimately reach the sources of ground-waters. The 

 chance that disease germs could survive this process in a 

 soil so impervious as to allow colon bacilli to appear only 

 in large samples of water, is however infinitesimal. 



An interesting contribution to the bacteriology of ground- 

 waters was made by the Massachusetts State Board of 



