An arresting example of the influence of heredity in disease is the development of the same chronic pathologic process in two or more members of a family when they reach a specified age. The family in the two cases herein reported furnishes such an example. In October 1937 Dr. J. Torrance Rugh of the department of orthopedics received a letter from two young men claiming that they "were very interesting cases" and would like to be studied and treated at this hospital. Through the courtesy of Dr. Rugh the patients, once admitted, were transferred to the medical service, where the following studies were conducted. Only the two principal cases will be dwelt on at length and simple mention made of relevant points in the histories of other members of the family. REPORT OF CASES Case 1.—History.— H. D., a white man, single, aged 27 (D-17 on the pedigree