Among experimental and clinical measures which are reported to raise the platelet count, surgical procedures, particularly splenectomy, have attracted much attention. This phenomenon is of interest for at least two reasons: First, the rise in the platelet count is more difficult to rationalize than many of the other thrombocytoses, such as those related to primary augmentation of the function of the bone marrow; second, the association of platelets with the clotting process has led to the loosely formulated belief that their increase after a surgical operation is connected with the occurrence of postoperative thrombosis. The first extensive clinical investigation of this subject to be reported was that of Hueck1 in 1925, who studied 100 varied surgical patients and found a brief fall in the platelet count postoperatively, followed by a rise to as much as three times the normal preoperative level. Hueck found the rise to begin at about