An ideal anticoagulant should be easy to administer, have a prolonged action and be free of harmful side effects. It should be relatively inexpensive and should not require frequent laboratory control for its safe administration. Neither heparin nor "dicumarol," as now commonly used, satisfies these requirements. Heparin1 has well known pharmacologic advantages over "dicumarol," but the necessity of repeated intravenous injection plus its high cost have acted as a deterrent to its common use. "Dicumarol"2 necessitates daily venipuncture and repeated prothrombin determinations, and it is difficult to control its action because of the fluctuation in its effects. Search for a more ideal anticoagulant has resulted in various preparations of heparin, all of which attempt to facilitate its administration. Thus Loewe and his co-workers3 used Pitkin's menstruum as a vehicle for subcutaneous use of heparin, and Stats and Neuhof4 injected intramuscularly a concentrated aqueous solution of heparin.