We have considered elsewhere1 the differentiation between initial atelectasis and resorption atelectasis, the degree of expansion of the lungs with the first breath, and the presence in premature babies of unexpandable pulmonary tissue, consisting of incompletely developed parenchyma.
The pathogenesis of the ordinarily recognized type of atelectasis in new-born and, particularly, premature infants forms the subject of this study.
The diagnosis of this condition as a complete and satisfactory cause of death, especially in premature infants, is widely accepted. It is obvious that when large areas of atelectasis are found in the lungs of a new-born infant who has died after exhibiting such evidences of imperfect respiratory function as constant or intermittent cyanosis, there must be a relation between the atelectasis and the anoxemia. The atelectasis may be accepted as the immediate cause of the anoxemia. It has seemed to us, however, that so long as the lung is