“…Transudation of constituents of blood plasma has been considered a factor in this process by many authors (Hadders and Dirken, 1955;Jarrett, 1957;van Breemen, Neustein and Bruns, 1957;Piper and Kleppe, 1958;Engelhardt, 1961). Alveolar capillary congestion and pulmonary oedema are commonly observed in lungs of infants with pulmonary hyaline membranes (Ziegler, 1957;Shanklin, 1959;Carone and Spector, 1960): this may be due to damage to the capillary wall resulting in increased capillary permeability. However, the exceedingly common, although not exclusive, association of hyaline membrane disease of the lung with prematurity has led some workers to believe that the lack of maturity of pulmonary tissue may play a role in such an increased permeability (Brummelkamp, 1958;Goebel, Koburg and Thelen, 1962).…”