We conclude therefore that this series of eleven lactose-negative organisms of the Friedländer type, grouped together by Perkins on the basis of fermentation reactions represents a single biological group. It can be distinguished from Bacillus aerogenes and other similar bacilli by cultural, fermentative, and serological reactions. There appears to be a close analogy between this group and Pneumococcus mucosus in the possession of a fixed cultural type, and the behavior toward immune serum. Both represent apparently a single biological group. Unfortunately no immune sera have been developed against the two strains that grew in moist and dry phases; it is possible that with immune sera for these light could be thrown on the relation suggested by Fitzgerald that the capsulated bacilli represent a parasitic development of the Bacillus coli group.

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