It has been shown by Gribetz that the excised lungs of infants dying with respiratory distress do not expand well,1and Cook et al2have demonstrated the reduced compliance of lungs of such infants during life. Gruenwald has indicated that the lungs of such infants will expand at pressures of 70 cm of water, but sustained pressures at this level are considered to be unobtainable during life in the newborn and very likely disruptive if achieved by external means.3The static pressures employed in this paper may have little relation to the relatively high pressures momentarily obtained during inspiration, or the short sharp rises in intratracheal pressure during resuscitatory procedures. Several years ago we demonstrated the nature of the expanded pattern of lungs of infants dying with hyaline membranes by injection, reconstruction, and corrosion techniques.4In these, it was found that the membranes appeared to obstruct