A boy, W. N., aged 2 years and 9 months, entered the Children's Medical Service at the Massachusetts General Hospital June 9, 1919. He was a full term baby, and for the first nine months was fed on drawn breast milk because his mouth would not open wide enough to permit him to nurse. Up to the end of the first year he was a very thin and poorly developed infant. He then commenced to gain rapidly in weight and has continued to do so up to the present time. His weight on entering the hospital was 24.82 kilos, (54 pounds, 9½ ounces). His mental development was that of a 10 months old infant. He recognized his family, but did not talk or feed himself, and was unable to stand alone. He was said to sleep well, to be happy and contented, and to have a good digestion.