P. E., a 23 month old infant, was admitted to Babies' and Children's Hospital, Cleveland, on Dec. 22, 1944. The complaint was soreness and swollen legs. Present Illness.—About Aug. 15, 1944, he fell. Soon afterward the right forearm became swollen and he complained of soreness along its radial aspect. On October 27, two days before admission to another hospital, a similar painful swelling began over the right shin which caused mobilization of the muscles of the right leg. He was irritable and anorexic. A tentative diagnosis of acute anterior poliomyelitis was made, but nothing was found to support it (J. A. T.). Roentgenograms of the bones showed them to be normal. The child improved quickly, and within six days the pain and the tenderness disappeared, although a limp persisted. A possible diagnosis of acute periostitis was made. The patient received an indefinite amount of penicillin over a period of