LATE STAGES OF PULMONARY HYALINE MEMBRANES OF THE NEWBORN.

In neonates suffering from pulmonary hyaline membranes and surviving the first few days i t has been observed that the membranes become infiltrated by histiocytes, fragmented and detached from the alveolar walls. This has been interpreted as evidence that the membranes are being removed [3, 10, 15, 181. In these cases a cellular reaction has also been described in the alveolar walls proper: proliferation of the alveolar epithelium and accumulation of fibroblasts. These latter features have been interpreted as a process of reparation, following previous damage to the alveolar ualls, and i t has been postulated, that such a damage probably is related to the development of hyaline membranes [3, 151. Studies with the electron microscope have revealed destruction of the alveolar lining and swelling of the endothelium in capillaries beneath the membranes in an early stage of the disease [5. 61. No permanent sequelae, however, have been recognized in the surviving cases [ll]. The reports hitherto published on the structure of pulmonary hyaline