Three years ago it was pointed out by one of us1 that the disease known as sickle cell anemia might better be named sickle cell disease, because anemia, though the best known and most frequent sign of this disease, is not the essential and not the most dangerous one. If this fact is not realized, diagnostic mistakes with disastrous consequences may occur. It is assumed that circulatory stasis in the small blood vessels of the internal organs is the primary and the most perilous consequence of the sickle cell trait (sicklemia), which is an inborn and constitutional abnormality of the red blood corpuscles encountered so far almost exclusively in Negroes. Patients afflicted with this disease do not, as a rule, die from anemia but may die from circulatory stasis in some vital organs. Since the sickling phenomenon—that is, the distortion of the red blood corpuscles of the affected persons—is