The clinical picture of acute rheumatic fever suggests strongly that the disease is due to sonic infectious agent. Although several microorganisms have been isolated from cases of this disease yet none has been obtained with sufficient frequency to establish conclusively a direct etiologic relationship. For this reason it seemed of interest to attempt to determine whether the disease might be due to some undiscovered virus which could not be isolated by the usual methods.
Defibrinated blood obtained from patients with rheumatic fever was injected into rhesus monkeys. Only typical cases were selected. The blood was taken before active treatment was begun and during the acute stage when the disease was spreading from joint to joint—the time when it seemed most probable that the causative agent would be present in the circulating blood. The blood was obtained in large test-tubes, defibrinated by means of glass beads and injected within three