Arthritis in Rats Caused by Pleuropneumonia-Like Micro-Organisms and the Relationship of Similar Organisms to Human Rheumatism

Abstract

The etiology of rheumatoid arthritis has remained obscure in spite of considerable investigation. The difficulty of its elucidation is increased by the fact that no experimental animal has yet been found in which it is possible to reproduce the disease or in which a strictly comparable disease has occurred spontaneously. Until comparatively recent, all attempts to produce arthritis in animals by the injection of microorganisms, either directly into joints, into the blood stream or by the establishment of foci elsewhere, have led to the development of joint disease which bears only slight resemblance to the typical changes of rheumatoid arthritis. The animal arthritis produced by bacteria is an acute process, usually markedly purulent, which may go on to a chronic state in which the late stages of the inflammatory process suggest, to a certain extent, the pathological changes found in rheumatoid arthritis, but the animal disease lacks many of the outstanding features of the human, particularly the phenomenon of recurrences, and also destruction of cartilage under a granulation tissue pannus. Recently there have appeared reports of spontaneous arthritis occurring in rats and mice, which have given new impetus to attempts to find an animal disease which resembles more closely rheumatoid arthritis and also to investi-