CHARACTERISTICS OF THE COLON-AEROOSENES GROUP 95 



tion of mannitol. The lactose fermenting KqucnVrs liuve always 

 been grouped together as B. cloacae, and we are inclined to 

 favor the retention of this arrangement until more conclusive 

 evidence can be produced to support a revision. 



Although we have only a small number of cultures which 

 produce only CO., in the anaerobic fermentation of dextrose, 

 this character indicates such a fundamental physiological de- 

 parture from the type that we have had no hesitation in 

 putting them in a class by themselves. 



Active liquefaction of gelatin and the fact that 8 of the 12 

 cultures included in this group failed to ferment lactose sug- 

 gests the identity of this type with the proteus group. The 

 three striking characteristics of the proteus group are the 

 failure to ferment lactose, the liquefaction of gelatin and the 

 formation of characteristic swarming colonies in gelatin. 

 Two-thirds of our cultures agree with the first character and 

 all with the second. The typical colony of proteus 011 gelatin, 

 according to the original description by Hauser, 25 has second- 

 ary colonies which appear in the medium around the original 

 colony. Evidently many cultures are classed as proteus which 

 are not known to form this peculiar type of colony. Herter 

 and TCJI Broeck~ mention one culture which did not form 

 swarming colonies until it had been passed rapidly through 

 a series of milk tubes and then plated on dextrose gelatin. 



We studied the colony fermentation of twenty-five liquefy- 

 ing cultures on 5 per cent gelatin at 20 C. There was a great 

 variation in the type of colony, and even in different colonies 

 by the same culture on a single plate. Only a few of the.se 

 twenty-five cultures formed what could be described as typical 

 proteus colon ies. In most cases the colony was round, with 

 a smooth margin and without out-growths of any kind. Lique- 

 faction appeared slowly, and the margin of the colony would 

 be unliquefied. There were many exceptions to this, some of 

 which are shown in Fig. 6. At a is shown a single strand 



25 Gustav. Hauser, uber Faulnissbacterien u. deren Bezielmngen zur Sep- 

 ticn'inie, Leipzig, 1885. 



26 C. A. Herter and C. Ten Broeck, A Biochemical Study of Proteus Vul- 

 &aris Hauser in Jour. Biol. Chem., 9, 6, pp. 491-511, 1911. 



