CHARACTERISTICS OF THE COLON-AEROGENES GROUP 



87 



pendent on the fermentation which produces the gas and it 

 is, therefore, additional and important evidence of the validity 

 of the distinction between the high and low ratio groups. 



Indol. The formation of indol has always been associ- 

 ated more closely with the fecal or B. coli type than with B. 

 aeroyenes. The correctness of this assumption is indicated 

 by the results shown in Table II and Fig. 2. Over 90 per 

 cent of the low ratio cultures formed indol against 26 per 

 cent for the high ratio cultures. This characteristic is evi- 

 dently subject to some variation and the percentage of posi- 

 tive results obtained depends in some measure on the technique 

 adopted. 



TABLE II 



PHYSIOLOGICAL REACTION OF NON-LIQUEFYING CULTURES, 

 ALL SOURCES 



A perfect correlation with the more basic characters could 

 not be expected but so far as the evidence goes it forms 

 another distinction between the low and high ratio group. 



