244 



L. A. ROGERS, W. M. CLARK AND H. A. LUBS 



and justifies our setting apart the low ratio organisms as distinct 

 from the more heterogeneous collection of high ratio organisms. 

 Whether or not this will ultimately prove to be sound judgment 

 the fact remains that it has been of great empirical value. But 

 we have not been content with using this basis of classification 

 alone. If it is a proper basis for a primary classification, there 

 should appear decided correlations between the gas ratios and 

 other cultural tests. As our studies have progressed, evidences 

 of such correlations have become stronger and are becoming more 

 clearly established as various tests become more rational and 



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Fig. 5. Graphic Representation' of the Salient Characters of the 

 Typhoid Colon, Aerogenes Group 



exact. Hulton (1916) in discussing our results says: ''In their 

 system of classification, the gas ratio formed the only basis of 

 differentiation; members classed within a single group display 

 marked differences in powders of liquefaction, indol-production, 

 and motility, but all agree in gas ratios." In view of the fact 

 that tests of indol production, gelatin liquefaction and motility 

 have not yet been placed upon an exact basis and because the 

 gas ratios correlate perfectly with the methyl red and Voges- 

 Proskauer tests in the present series, we should perhaps be wilhng 

 to have it understood that the gas ratios formed the only basis of 

 primary classification. This, however, would hardly be a correct 



