BACTERIA OF THE COLON TYPE IN HUMAN INTESTINES 245 



statement of our views since we have shown by biometric treat- 

 ment correlations among other cultural characteristics which are 

 quite as good as those obtained in other schemes of classification. 



Khgler (1914), as the result of a study of 80 cultures in the 

 collection of the American Museum of Natural History, proposed 

 a classification based upon the ability to ferment certain sugars 

 and alcohols. This was a step in advance in that it was based on 

 correlated characters. We are not ready to admit, however, 

 that the fermentation of polysaccharides is in itself a sufficiently 

 fundamental character to be used for major divisions of a large 

 group. 



Levine (1916b) has proposed a classification of the colon- 

 aerogenes group in which particular attention is given to those 

 cultures which are included in figure 5 as B. coli. Six species are 

 made of this group, one of which includes two varieties. The 

 separations are made on sucrose fermentation, motility and the 

 fermentation of salicin, dulcitol and glycerol. We have always 

 considered that B. coli as represented in figure 5 is comparatively 

 a homogenous group and that the differences indicated by varia- 

 tions in sugar fermentations are not of specific rank. On the 

 other hand, we have looked upon B. aerogenes, which Levine 

 includes as a single species, as a heterogenous group much in 

 need of further division. 



The greatest value of definite knowledge of the characteristics 

 of a class of organisms lies in the ability which it gives us to 

 arrange these organisms in orderly groups. Ever since the 

 beginning of the science bacteriologists have attempted to do this 

 and as the knowledge of bacteria has advanced new systems of 

 classification have been proposed, many of them differing radi- 

 cally from their predecessors. 



The cumulative result of these attempts to create order has 

 brought such confusion that we have hesitated to apply our results 

 to any system of classification for the colon-aerogenes group. 

 We feel, however, that the data which have accumulated in the 

 last few years have sufficient value to warrant us in outlining their 

 possible application to taxonomic problems. While there is no 

 generally accepted scheme of classification for the typhoid-colon 



