The rarity of reported cases of arteriovenous aneurysm of the innominate artery is amazing. This is explained by the fact that the etiology is usually traumatic and that trauma sufficient to penetrate the thorax and lacerate the innominate artery is usually fatal.
Exploration of the "Quarterly Cumulative Index Medicus" and the "Index Medicus" in their entirety, a search of cross references and collateral reading back to Hunter's monograph in 1757,1 and checking numerous case reports has yielded but two cases.*
Twelve series of reported cases of aneurysm were studied f (Table). Various modes of selection were employed in these series, i. e., surgical cases, traumatic aneurysms, radiographically studied cases, etc. Therefore the figures obtained do not represent the absolute incidence of aneurysms. The venerable analysis of aneurysms by Crisp, in 1947,4 was the most extensive work. He collected 531 cases of aneurysm and reviewed a group of 364 at the