Abstract
The MEF-1 strain of poliomyelitis virus was adapted to the intravenous route in mice by criss-cross passages between mice and tissue cultures. 107 ID50 doses for tissue cultures were required to produce 50% response (paralysis or death) after in-travenous inoculation in 4-6 weeks old CFW mice. The intraven-ously inoculated virus disappeared from the serum within 24 hours but was recovered from spinal cord, brain and feces.