1. In two, and possibly four, of six transmission series of rabbits inoculated in the beginning with the blood of apparently normal rabbits a virus was recovered having the same properties as that recovered from series originally inoculated with material from rheumatic fever patients. The virus was immunologically identical with Rivers-Tillett Virus III and with that obtained from the rheumatic fever series. In conducting the control series precautions were taken to prevent infection of rabbit stock from known sources of the virus.
2. Treating rabbits with benzene does not appreciably increase their susceptibility to infection with the virus.
3. The virus is probably a parasite of the domestic rabbit but up to the present time the natural course of the infection in that animal is unknown.