By W. N. POWELL, M.D., J. G. RODARTE, M.D., AND J. V. NEEL, PH.D., M.D. A LTHOUGH in recent years the blood disorders sickle cell disease and thalassemia have both been studied extensively from the genetic standpoint, thus far the simultaneous occurrence within a single family group of the genes responsible for these two diseases has not been reported in the medical literature of the United Sta...