ANY part of the pleura-covered lung which protrudes beyond the normal boundaries of the thoracic cage and invades the subcutaneous tissues can rightfully be designated as a true hernia. True lung hernia should not be confused with evisceration or prolapse, an error not infrequently made by early writers. Lung hernia is a very rare condition; up to the present time, less than 200 cases have been reported in the literature. Because of its rarity, clinicians of wide experience have had little opportunity to observe it. Much information in the literature is inaccurate and confusing and, therefore, some early reports are not dependable. Several names have been applied to lung hernia, as pneumonocele, pneumocele, and pulmonary hernia. Considering the great number of stab and bullet wounds in warfare and civilian life, and crushing injuries of the chest, it is surprising that lung hernia is not more frequent. In an extensive war experience with chest wounds, Makins observed one case, while Adams reported five out of 20,000 chest wounds in the Russian-Japanese War (1). It is also noteworthy that, with frequent fractures of the ribs, pneumothorax rarely occurs. In a study of 89 cases of fractured ribs requiring hospitalization, 16 were treated for other complications but only one instance occurred in which pneumothorax resulted (2). History As early as 1891, Rolandus published a report of the first case operated upon for lung hernia (3). Chassier mentions herniated lung and was one of the first to accord it special consideration (4). Cloquet, in 1819, reported a case of a young man, age 32 years, crushed under a gun carriage, who made a good recovery (5). Morel-Lavallée, who collected 32 cases, gave us a very comprehensive classification (6). Lake mentions a case of lung hernia caused by the handle of a wheelbarrow penetrating the side of the chest (7). Dufour reports a case of traumatic hernia cured without operation, after much loss of blood (8). In 20,000 wounds in the War of the Rebellion, only seven lung hernias were reported. Cockle published a case of double pulmonary hernia (9). Lewtas (10) and Hirschsprung (11) each reported a case of congenital hernia. Spontaneous pneumocele from violent exertion in weight lifting was reported by Masoti (12). Hagentorn (13) mentions pneumotomy in pneumocele. In 1893, Pitt (14) affirmed that the protrusion of hernia may occur at the time of trauma or any time later. Lopez (15) reported resection of the lung for hernia, with recovery. Tuffier (16) mentions resection of the lung and Knox (17) reported two cases of hernia of the lung into the neck. From 1895 to 1904 several cases of hernia of the lung and its treatment were reported (18, 19, 20, 21, 22). Vulpius (23) reported a case of traumatic hernia of the lung which, five weeks after plastic operation, was discharged, cured.