Primary tumors of the thymus are uncommon. Primary carcinoma is an exceedingly rare variety of thymic new growths, hence any definitely established neoplasm of this type should be recorded. A few years ago I had the opportunity of studying a case of carcinoma of the thymus, arising from Hassall's corpuscles, with metastasis to many organs. It is from the clinic of Dr. Henry A. Christian, to whom I am indebted for his permission to use the clinical data. REPORT OF CASE History. —The patient, a salesman, aged 42 years, entered the hospital Sept. 21, 1920, complaining of pain and stiffness in the lower part of his back. He was well up to June 1, 1920, when his back low down felt stiff and sore on rising in the morning. After moving around an hour or two, this stiffness and soreness left, only to return in the evening. The diurnal remissions