The valiant efforts made by many investigators to advance the treatment of diseases and injuries of blood vessels have been hampered by thrombosis and clotting in these structures. The uncontrollable factor leading to failure in many cases is not the giving way or leaking of suture lines or weakness, dilatation or stenosis of blood vessels but is occlusion of the vessels by thrombosis. The discovery of the anticoagulant heparin by Howell1 in 1916 was therefore an epoch-making event. More recently, experiments by Murray and his co-workers2 demonstrating that heparin would also prevent thrombosis were of importance in developing this subject. The final purification of heparin by Best and by Charles and Scott3 made it safe to give this substance to clinical patients.
Heparin is a strong organic acid, probably a mucoitin trisulfuric acid. In addition to preventing clotting, it has an important effect on the