Adaptation of ‘ B ’ Virus to the Swiss Albino Mouse

SUMMARI’: The ‘B ’ virus (strain no. 1) of the 68th rabbit passage has been successfully transmitted to Swiss albino mice and carried through ten passages in this species by intracerebral inoculation. This virus produced symptoms of irrita-bility and involvement of the central nervous system in these mammals. Paralysis occurred in mice from the 6th to the 10th passages. Virus-bearing material from the 10th intracerebral mouse brain passage upon being injected intradermally into unvaccinated rabbits produced paralysis but had no effect on rabbits previously immunized against ‘ B ’ virus. The ‘By virus (strain no. 1) was isolated from the spleen and central nervous system of patient B and maintained since the original isolation in 1932 by serial passage in rabbits. This virus is extremely pathogenic for rabbits by most routes of inoculation. Following intracutaneous injection, a haemorrhagic necrotic area develops around the site of inoculation. About 1-2 days before paralysis occurs, most rabbits exhibit a tendency to bite the local lesion. Previous workers have found that the virus killed mice of about 2 weeks o