Perforation of the interventricular septum of the heart, aside from cases of congenital malformation, in the great majority of cases is due either' to rupture of an interventricular aneurysm or to ulcerative endocarditis. Perforation from other causes, such as rupture of a hydatid cyst, 1 has been described but such cases are relatively very rare. CARDIAC ANEURYSMS Cardiac aneurysms have long been the subject of reports in the literature, and many excellent monographs have been written on the subject. It is said to have been first described by Guzman Galeati in 1757. 2 Also Thurman 3 reports a case from the manuscripts of John Hunter described in 1757. The first monograph was written by Breschet in 1827. 4 Pelvet, 5 in 1867, gave an excellent discussion of the subject. Bourland, 6 in 1904, without giving references, reports having collected 147 cases from the literature. Osler and McCrae 7 refer to 135 cases, and Friedlander and Isaacs 8 reported