The term "sickle cell anemia" is used to designate two conditions: (1) a hereditary predisposition to anemia occurring only in the negro race and characterized by the development of a crescentic distortion of the red corpuscles under certain conditions, and (2) a chronic, severe anemia affecting only negroes with this predisposition, characterized by remissions and exacerbations, hemolytic jaundice, episodes of abdominal pain, joint pains without inflammation and a tendency to ulcer of the leg. In 1910 Herrick1 reported a case of a negro who had jaundice, a history of ulcer of the leg, leukocytosis and severe anemia associated with the occurrence of crescentic red corpuscles in the stained and wet smears of the blood. Some of the crescentic poikilocytes were nucleated. Washburn2 reported the second case with essentially the same clinical picture, and Cook and Myer,3 the third. Cook and Myer believed that the sickle distortion, which he regarded as