When the entire body of dogs was exposed to 450 units of Roentgen irradiation a hemorrhagic syndrome developed which was characterized by thrombo-cytopenia, prolonged clotting and bleeding times, and neutropenia.
The prothrombin time remained normal until about 24 hours before death. The calcium, phosphorus, and magnesium levels were not altered. Fibrinogen was present but syneresis was poor.
Toluidine blue and protamine sulfate, substances which can inhibit the biologic action of heparin, restored the clotting time to normal.
The hemorrhagic state was not materially altered by transfusions, vitamin K, or vitamin C.
Toluidine blue and protamine sulfate were ineffective in the control of hemorrhage produced by dicumarol.
The defect responsible for bleeding after irradiation appeared to be the presence in the circulation of an anticoagulant whose properties, so far as tested, were indistinguishable from those of heparin.