Other Intestinal Bacteria. 167 



It is certain that in the intestine these atypical forms 

 are less common than the colon bacillus itself, bearing to 

 it indeed very much the relation implied in Vincent's term, 

 satellites. Houston (1903*) examined in detail loi 

 cultures of coli-like microbes isolated from feces, and 

 found that 72 per cent of the cultures were typical in all 

 respects, while 11 per cent more differed only in being 

 non-motile. The remaining 17 per cent were atypical, 

 reacting abnormally to milk, indol, neutral red, litmus 

 whey or Capaldi and Proskauer's medium. In a later 

 investigation, Houston (1904) made a careful study of 

 the distribution of the atypical forms in feces, sewage, 

 polluted water, and the filtered water-supplies of London. 

 According to his ingenious system of nomenclature, 

 "fl" indicates an organism which produces green 

 fluorescence in neutral red broth; "ag," one which forms 

 acid and gas in lactose media; "in," one which produces 

 indol; and "ac," one which acidifies and clots litmus 

 milk. The combination of all these properties gives 

 "Flaginac," or typical B. coli; "aginac," is a form which 

 •fails to reduce neutral red; "flagac," one which fails to 

 form indol, etc. "Flaginac" B. coli form the great 

 majority of coli-like microbes in feces, but Houston foimd 

 that in filtered water they are outnumbered by at)^ical 

 forms, of which he recognized thirty-five distinct types. 



On the whole, all the evidence tends to the assumption 

 that the atypical forms, or "paracolon bacilli," generally 

 represent weakened strains from the intestinal B, coli 



