Mary W., aged seven months, was taken suddenly sick with high fever the night of July 7. No cause for the fever could be made out. The temperature ran between 103 F and 105 F up to the time she was seen in consultation, July 14. The physical examination had always been negative. She had had a slight cough in the beginning. The bowels had moved regularly and the movements had been normal. She had always been conscious, but during the last two days had seemed tender all over and had held her head backward. During the last two or three days the urine had left greenish-yellow spots on the diapers.