The Significance of B. Coli in Water. 117 



aroused Professor Kruse's pupil, Weissenfeld, to a pub- 

 lication, 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 pathogenicity 

 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 fre- 

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

 have shown that there is in general no correlation between 

 pathogenic power and direct or indirect intestinal origin. 

 On the other hand Weissenfeld's work entirely fails to 

 show that the colon bacillus, pathogenic or non-patho- 

 genic, is a normal inhabitant of unpolluted waters. In 

 the first place it should be noted that the characters used 

 by this investigator for defining the " so-called Bacterium 

 coli " were absolutely inadequate. He classed under 



