Abstract
1. The spiral organism isolated from a wild rat has proved identical with that from a human case of rat-bite fever in Mexico City. 2. Rabbits can easily be infected with these organisms. 3. The subcutaneous inoculation of them is followed after 3 to 5 days by a local edema, induration, and inflammation: primary lesion. 4. About 8 days after the appearance of the primary lesion, edematous swellings and inflammation appear on the head and genitals: secondary lesions. 5. The organism can be transmitted from rabbit to rabbit by coitus. 6. Protective antibodies are to be found in the blood of infected rabbits at a time when the local lesions are still active. The peculiar character of certain of the lesions is probably due to the escape of the antibodies from the blood stream. 7. The organism belongs to the genus Treponema.