288 CHEN CHONG CHEN AND LEO F. RETTGER 



6.2-6.5. This would indicate that variation within certain limits 

 in the hydrogen ion concentration is to be expected. After 39 

 replatings the above-mentioned 4 strains still failed to correlate, 

 however, in so far as the methyl red test and the Voges and 

 Proskauer reactions are concerned, both being positive. It is 

 unfortunate that we were unable at the time to make exact gas 

 determinations on these 4 strains, since Clark and Lubs have 

 claimed that "when a perfectly clear-cut correlation fails, there 

 is generally found some abnormality in gas-production. . . ." 



All of the 4 peculiar strains gave a pronounced Voges and 

 Proskauer test and were able to attack the purin ring in uric 

 acid; hence, in so far as these two reactions are concerned these 

 organisms resembled typical B. aerogenes. 



Rogers and his associates reported that the majority of their 

 atypical strains gave a pH value ranging from 5.6 to 6.0, and that 

 most of them (11 out of 16) were Voges and Proskauer positive. 

 Repeated replating might have materially reduced their number 

 of atypical strains, as the pH values given by them were so near 

 the border line of the methyl red indicator range, and as a small 

 variation in the hydrogen ion concentration must be expected 

 of all bacteria. 



CORRELATION OF CHARACTERS 



Chart VIII presents graphically the results obtained in the 

 study of the various characters of the 447 aerogenes and 173 

 fecal strains of coliform bacteria. The tests embraced the methyl 

 red, uric acid and Voges and Proskauer reactions, deportment 

 towards glucose, lactose, sucrose and adonitol, indol formation 

 and gelatin liquefaction. As a matter of brevity, the results 

 obtained with the 20 coli strains from soil and the 4 atypical 

 strains are not presented here in chart form. They differ little 

 from the above, aside from a difference in indol production and 

 adonitol fermentation, and the points already mentioned with 

 reference to the methyl red, uric acid and Voges and Proskauer. 



It will be observed in the accompanying chart that perfect 

 correlation, exists for both the aerogenes (447) and the fecal coli 



