“…It may be that the retention of pus gives rise to bronchial dilatation by pressure from the inside (Laennec 30 ). Broncho-stenosis causes atelectasis, leading to a markedly increased negative pleural pressure, and a radial traction is exerted on the bronchial walls (Jacobaeus and Westermark 31 ). If the atelectasis is not cured, induration follows; shrinkage of the connective tissue also causes a radial traction on the bronchial walls.…”