So ELEMENTS OF WATER BACTERIOLOGY. 



recently examined by one of ourselves (Prescott, 1902 a ; 

 Prescott, 1903) 25 were found to give the reactions of B. 

 coli. These organisms were isolated chiefly from cereals 

 and products of milling, such as flour, bran, corn-meal, 

 oats, barley, etc., while others were in technical use for 

 producing the lactic fermentation. There is no evidence 

 that any of these organisms were of intestinal origin, and 

 yet they possess all the characters of typical colon bacilli, 

 even to the pathogenic action when inoculated into 

 guinea-pigs. These results explain the results of Klein 

 and Houston (Klein and Houston, 1900), who reported 

 the finding of typical colon bacilli in 3 out of 24 samples 

 of wheat and oats obtained from a wholesale house; rice, 

 flour, and oat- meal bought at two different retail shops 

 gave B. coli on all three cereals in i case and on none in 

 the other. In Germany, Papasotiriu (Papasotiriu, 1901) 

 was meanwhile carrying on almost exactly similar inves- 

 tigations to Prescott' s, with identical results. 



What then does a colon test prove? Obviously (i) the 

 presence of a colon bacillus which has come directly from 

 the intestine of some animal, or (2) of a colon bacillus 

 which has come indirectly from an animal, or (3) of a 

 saprophytic "lactic- acid bacillus" which gives the same 

 biochemical reactions. This immediately raises the 

 interesting questions, Is it possible that the lactic-acid 

 bacilli have been indirectly derived from animal intes- 

 tines, having " escaped from cultivation/' as the botanists 

 say? Or is the converse true, namely, that all colon 

 bacilli are simply lactic-acid bacteria which have found 



