The effect of unilateral increase in intrapleural tension, as seen in pleural effusion and spontaneous pneumothorax, on the position of the mediastinal organs, had been well known long before artificial pneumothorax was added to the armamentarium of phthisiotherapy. Indeed, one of the most important signs of pleural effusion and spontaneous pneumothorax is displacement of the heart toward the sound side. Grocco's triangle as a sign of pleural exudate is also supposed to depend on the shifting of the mediastinal contents toward the unaffected side.
Most of the information regarding the effect of increased intrapleural tension on the mediastinum gathered in previous years was, however, mainly the result of observations in cases of pleural effusion. Nithc,1 in a rather instructive article based on experimental evidence, describes most lucidly the anatomy of the mediastinum, laying particular stress on those vulnerable points which are most likely to yield to increased intrapleural pressure.