A CHANGE IN RABBIT FIBROMA VIRUS SUGGESTING MUTATION : I. EXPERIMENTS ON DOMESTIC RABBITS.

A strain of rabbit fibroma is described causing in inoculated animals acute inflammatory lesions very different from the fibroma-like growths induced by the original strain. The new inflammatory strain cross-immunised with the normal strain but not with various other viruses. Efforts at changing one strain into the other were unsuccessful. Another, referred to as the changed, strain produced lesions of mixed character, partly inflammatory, partly fibromatous; it continued to behave in this way through numerous passages. An artificial mixture of inflammatory and fibromatous viruses behaved in all respects like the changed strain. Discussion of the significance of the findings is reserved for a separate paper (3) where the facts can be considered in relation to those described by Shope (2).