Experimental Pulmonary Arterial Occlusions: Acute Cor Pulmonale Simulating “Obstetrical Shock” of late Pregnancy**This investigation was supported in part by the Medical Research and Development Board, Office of the Surgeon General, Department of the Army, Contract No. DA-49-007-MD-194, while Dr. Schneider was Assistant professor of Physiology and Pharmacology, Wayne University College of Medicine.