232 Thèse de Paris, 1882.
233 Ibid., 1841.
In tubercular cases perforation of the lung may occur at any period of the disease; the most frequent time, however, is that of the softening or while excavations are being formed, where adhesions have not yet protected the two sides by binding them together with neo-membranes. It may come from a small cavity. Andral met with cases where only a few tubercles existed. Townsend reported a case where one tubercle burst immediately under the pleura. The superior lobe of the lung is where the perforation generally occurs, because it is there that the tubercular lesion ordinarily commences and is most advanced (Louis). It is least frequent in chronic fibroid phthisis and most often met with in acute pneumonic phthisis. Douglass Powell234 reports cases where sinuses extended from cavities, and finally burst into the pleura. Sometimes the rupture occurs at the base of the superior lobe, about the third or fourth rib; it may happen, however, at any point of the lung; it has even occurred at the base of the lung lying on the diaphragm (Houghton235).
234 Med. Times and Gaz., Jan. and Feb., 1869.
235 Cyc. Pract. Med., vol. iii.
Saussier236 shows by the following table the relative frequency of the principal causes of pneumothorax in 131 cases:
| Pneumothorax | with | phthisis | 81 |
| " | " | empyema | 29 |
| " | " | gangrene | 7 |
| " | " | pulmonary emphysema | 5 |
| " | " | apoplexy | 3 |
| " | " | hepatic fistula | 2 |
| " | " | hydatids | 1 |
| " | " | hæmothorax | 1 |
236 Thèse de Paris, 1841.
Empyema ranks second as a producing cause of pneumothorax. Ordinarily, by direct necrosis of the parietal pleura, an orifice is made through which the pus is evacuated through the bronchi, and air in inspiration enters the pleural cavity by the bronchial fistula. Pyothorax is converted into pyo-pneumothorax. The valvular opening may, however, be closed by inspiration so that air cannot enter, or adhesions may limit a portion of the pleura, and then we have a circumscribed pneumothorax. Empyema, by producing ulceration of the thoracic walls and pointing exteriorly (emphysema necessitatis), leaves fistulæ through which air enters the pleural cavity.
Gangrene of the lung by sloughs allows air to penetrate. Bronchiectasic cavities sometimes become the seat of putrefactive changes and ulcerations through the lungs into the pleura. Infective emboli being arrested in the smaller peripheral branches of pulmonary arteries, air enters the cavity; it is thus that pneumothorax arises in various kinds of surgical diseases when infective emboli pass into the circulation (Fraentzel). Flint237 reports a well-marked case of pneumothorax, lasting less than one month, where there was every reason to suppose that it had been caused by rupture from interstitial emphysema. W. T. Gardner had previously reported a similar case. Saussier found emphysema was a cause in only 5 out of 131 cases. Fraentzel speaks of emphysema as rarely being a cause. Perforation of the oesophagus, ulcerative, cancerous, or traumatic from the use of bougies, produces pneumothorax. Suppurating bronchial glands—a case of which was met with by the author—bursting into the cavity produce pneumothorax. Hydatids of the lungs, abscesses of the abdomen, sometimes coming even from the cæcum and from the liver, burst into the pleural cavity and introduce air. Echinococcus cysts of the liver are occasionally emptied into the pleural cavity.