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Imperfect expansion of the lungs at birth, giving rise to Cyanosis pulmonalis. A similar condition is observed in lungs which have received air, and in a distinctly lobular form. This is regarded by Dr. W. T. Gairdner as, in all probability, a secondary lesion, and dependent, in the majority of instances, on a catarrhal condition of the bronchial tubes. It is called, by him, pulmonary collapse, or collapse of the lung, and has received the name apneumatosis from Fuchs.

Imperfect expansion of the lungs with consequent persistence of their fetal condition after birth.