622 Bacillus Coli 



not a single species, but a group of bacilli too similar to be differen- 

 tiated into groups, types, or families by our present methods. 



In order to establish a type species of Bacillus coli communis, 

 Smith* says: 



"I would suggest that those forms be regarded as true to this species which grow 

 on gelatin in the form of delicate bluish or more opaque, whitish expansions with 

 irregular margin, which are actively motile when examined in the hanging drop 

 from young surface colonies taken from gelatin plates, which coagulate milk 

 within a few days; grow upon potato, either as a rich pale or brownish-yellov/ 

 deposit, or merely as a glistening, barely recgonizable layer, and which give a 

 distinct indol reaction. Their behavior in the fermentation-tube must conform 

 to the following scheme: 



' ' Variety a: 



"One per cent. dextrose-bouiUon (at 37°C.). Total gas approximately J^; 

 H : CO2 = approximately 2:1; reaction strongly acid. 



"One per cent, lactose-bouillon: as in dextrose-bouillon (with slight varia- 

 tions) . 



" One per cent, saccharose-bouillon; gas-production slower than the preceding, 

 lasting from seven to fourteen days. Total gas about %; H : CO2 = nearly 

 3:2. The final reaction in the bulb may be slightly acid or alkaline, according to 

 the rate of gas-production (B . coli communior, Dunham) . 



"Variety /3; 



"The same in all respects, excepting as to its behavior in saccharose-bouillon; 

 neither gas nor acids are formed in it." 



DIFFERENTIAL CHARACTERISTICS 



Typhoid Bacillus Colon Bacillus 



Bacilli usually slender. Bacilli a little thicker and shorter. 



Flagella numerous (10-20), long, and Flagella fewer (8-10) (peritricha). 



wavy (peritricha). 



Growth not very rapid, not particu- Growth rapid and luxuriant. This 



larly luxuriant. character is by no means constant. 



Upon Eisner's, Hiss', Piorkowski's, and Upon Eisner's, Hiss', Piorkowski's, and 



other media gives characteristic ap- other media gives characteristic 



pearances. appearances. 



Upon fresh acid potato the so-called Upon potato a brownish-yeUow distinct 



"invisible growth" formerly thought pellicle. 



to be differential. 



Acid-production in whey not exceeding Acid-production well marked 



3 per cent. Sometimes slight in or- throughout. 



dinary media, and succeeded by 



alkali-production. 



Grows in media containing sugars with- Fermentation with gas-production well 



out producing any gas. marked in solutions containing 



dextrose, lactose, etc., the usual for- 

 mula being H : CO2 = 2:1. 



Produces no indol. Indol-production marked. 



Growth in milk unaccompanied by Milk coagulated. 



coagulation. I 



Gives the Widal reaction with the ser- Does not react with typhoid blood. 



um of typhoid blood. 



Colon Bacillus in Drinking Water. — Much importance attaches to 

 the presence or absence of colon bacilli in judging the potability of 

 drinking waters. 



* " Amer. Jour. Med. Sci.," 1895, no, p. 287. 



