Serologic reactions of oral gram negative anaerobic bacilli. 
Serological reactions were performed using hyperimmune rabbit antisera and antigenic preparations of Leptotrichia buccalis, Fusobacterium fusiforme, and Fusobacterium polymorphum.  All tests indicated that there was serologic cross reactivity between the two Fusobacterium species.  No cross reactivity could be detected between the Fusobacterium species and L. buccalis.  The findings suggest that F. fusiform and F. polymorphum are similar in their immunogenicity, and that the grouping of these two organisms as F. nucleatum may be justified.