'Pleural Rings' or Annular Shadows in the Lungs

In discussing Annular Shadows (Pleural Rings) in the lungs it is necessary to define our terms. My remarks will be confined to the thin walled air containing rings, and do not apply to ordinary tuberculous cavities. Personally, I prefer to call these rings “air cysts,” as they certainly represent encysted air. They are, undoubtedly, cavities, and stereoscopic views satisfy me that they are in the lung and not between the lung and the chest wall (Radiogram 4). I beg to submit the following theory of their mode of origin. A small bronchus or bronchiole weakened by disease and strained by coughing, becomes perforated and allows air to leak into the connective tissues of the lung. It does not become an interstitial emphysema but a single bubble of air. Let me for a moment draw your attention to the Bramah Press, with which you are doubtless all acquainted. Water communicates with two cylinders, one of which is considerably larger than the other. Watertight pistons are fitted to both. Any force or pressure app...