SIGNIFICANCE OF COLON GROUP IN WATER 145 



of the colon group isolated by them from water kill 

 a guinea pig, even when i or 2 c.c. were injected intra- 

 peritonally. The authors, therefore, considered patho- 

 genicity as an attribute belonging only to the true 

 B. coli of the intestine. This paper aroused Professor 

 Kruse's pupil, Weissenfeld, to a publication, in which 

 the position of the Bonn school was carried to an 

 extreme. Weissenfeld reported (Weissenfeld, 1900) the 

 analysis of 30 samples of water supposedly pure, 

 and of 26 samples considered to be contaminated. In 

 each case a single centimeter sample was first incubated 

 in Parietti broth, and if no growth occurred, larger 

 samples of half a liter or a liter were examined. Colon 

 bacilli were found in all the samples; and the patho- 

 genicity varied independently of the source of the water. 

 The author concluded that " the so-called Bacterium 

 coli may be found in waters from any source, good or 

 bad, if only a sufficiently large quantity of the water 

 be taken for analysis." 



With regard to the question of pathogenicity as a 

 diagnostic test for intestinal B. coli, there is little doubt 

 of the correctness of Weissenfeld's conclusions. This 

 property is so variable as to have no important value. 

 Colon bacilli freshly isolated from the intestine are 

 frequently non- virulent, and Savage (1903*) and others 

 have shown that there is in general no correlation 

 between pathogenic power and direct or indirect intes- 

 tinal origin. On the other hand Weissenfeld's work 

 entirely fails to show that the colon bacillus, pathogenic 

 or non-pathogenic, is a normal inhabitant of unpolluted 

 waters. Even his own results, if the quantitative rela- 



