Abstract
In order to elucidate the stability of the occured change on the properties of the tsutsugamushi disease rickettsia by contineous action of small amount of chloramphenicol in the body of mouse, the author investigated the stability of the varied rickettsia using that rickettsia as the antigen in the complement fixation test. As the result of this investigation, the occured change on the properties of the rickettsia found to be turned back to that of the original rickettsia by serial passage through normal mouse at least 7 generations.
