Functional overactivity of the spleen, or hypersplenism, includes a variety of hematologic syndromes with multiple clinical pictures based on perverted activity of the spleen with respect to its capacity to destroy various blood cells. Hypersplenism, which was first described by Wiseman and Doan,1has in recent years assumed increasing importance in the field of hematology. Recognition of the fact that, in certain persons, the spleen may become hyperfunctional with respect to destruction of blood cells has resulted in ever increasing indications for splenectomy. The clinical syndromes that have been described under the heading of hypersplenism include chronic splenic neutropenia, acute splenic neutropenia, acute and chronic splenic panhematopenia of both congenital and acquired types, familial hemolytic icterus and idiopathic thrombopenic purpura. The depleted cell values of so-called aplastic or hypoplastic anemia may be intensified by increased or normal activity of the spleen. Furthermore, certain diseases involving the spleen, such as