The purpose of this paper is to report another case of defects in the membranous bones, diabetes insipidus, and exophthalmus, the seventh now in the literature, and to discuss some of the factors bearing on this disease. REPORT OF CASE History. —A girl, aged 7 years, first came under observation June 27, 1919. Her parents were well; there were one older and two younger children, and no miscarriages. Patient was a full term baby, normal in the first year. In the second year she was weak and did not develop as did the other children, since when she has been underweight and underheight. At 6 years a tooth became infected, followed without pain by a discharge from the left ear, and an infection of the left mastoid, which was opened and drained in October, 1918. Following this, her mouth became very sore with a bullous eruption on the gums, necessitating