Gager,1in 1928, collected 402 cases of dissecting aneurysm from the German and the English literature, five of which were diagnosed ante mortem. More recently, Vaughan and Irons2have each diagnosed a case ante mortem. Ettling2has correctly diagnosed six cases of traumatic dissecting aneurysm before death. The clinical features have been excellently described by Gager,1the four primary ones being a sudden onset usually following strain; a severe, continuous pain like that of coronary occlusion, and often with significant distribution in that it progresses with the dissection; anomalies of the circulation such as inequality or absence of arterial pulsation in various regions, and the effects of disturbed circulation in other organs or parts of the body. Four fifths of the instances occur after the age of 40, the incidence being twice as great in men as in women. Sixty-five per cent of the victims die