1.The serological characteristics of D. granulomatis, with special reference to antigens which it has in common with members of the tribe Eschericheae were studied, employing the sera of rabbits immunized against these organisms.
2.Reciprocal absorption studies carried out with these sera, together with other observations, suggest that the serological similarity between D. granulomatis and certain K. pneumoniae organisms is due to a single common capsular antigen, which is a haptene.
3.Since numerous organisms, differing in taxonomic position, share common antigens, there does not appear to be sufficient grounds, at present, for changing the taxonomic position of D. granulomatis to bring it closer to organisms to which it shows a serological relationship.
4.Morphological and cultural differences still separate D. granulomatis from the Klebsiella genus, and the explanation of these differences on the basis of mutation still requires further evidence, particularly with reference to the role of a mutant in producing the pathological reaction of granuloma inguinale.
Division of Preventive Medicine, University of Tennessee College of Medicine, Memphis 3, Tennessee.