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CHEN CHONG CHEN AND LEO F. RETTGER 



which contains the nitrogen. All of the soil coli strains failed 

 to attack the xanthine, and hence reacted like typical B. coli. 

 Further investigation may show that xanthine may be superior 

 even to uric acid for differentiating these two types of bacteria, 

 unless types intermediary between coli and aerogenes exist which 

 in uric acid medium are sharply distinguished. With two ex- 

 ceptions, both types of bacteria failed to develop in the caffeine 

 and the theobromine medium. The results with the xanthine, 

 caffeine and theobromine media are shown in the following table. 



Table giving results with xanthine, caffeine and theobromine media 



FERMENTATION OF GLUCOSE, LACTOSE, SUCROSE, ADONITOL AND 



DULCITOL 



It was at first intended to classify the present collection of 

 strains according to McConkey's primary divisions, on the basis 

 of fermentation of glucose, lactose, sucrose and dulcitol. Ado- 

 nitol was also employed because of the claims of Rogers and others 

 that the so-called fecal and non-fecal types of B. aerogenes can be 

 differentiated in this way. Owing to our inability to obtain 

 sufficient dulcitol the classification study with McConkey's four 

 sugars was incomplete. The results are presented in the fol- 

 lowing table. 



