To the Editor.—The article by Ambrus et al in the February issue of the Journal (127:189, 1974) invites attention to plasminogen deficiency as the cause for hyaline membrane disease (HMD). Presumably, the authors refer to more severe forms of the respiratory distress syndrome (RDS) that occurs with varying severity and may very well involve several causes.
For many years, as I witnessed deliveries, I have speculated on the effect of certain physiological phenomena of the birth process. In particular, in vertex delivery, the head emerges while the chest, in the birth canal, is under considerable pressure. This results in the expulsion of an astonishingly large amount of fluid from the infant's nose and mouth—fluid that has been secreted into or by the lungs, amniotic fluid that may have been aspirated, and contents of the upper air passage. When the chest is now delivered, the elastic recoil triggers the