In recent years massive collapse (atelectasis) of the lungs has ceased to be regarded as a rare occurrence, and this is largely due to the universal use of roentgenography, which has become so indispensable an adjunct in clinical diagnosis. The type of collapse of the lung now under consideration is that which occurs in a lung that was previously normally aerated, with normal anatomic landmarks, in which a sudden cessation of the intake of air, with a consequent atelectasis of the alveolar tissue results from some disturbance in the bronchial tree as obstruction, occlusion or obturation. This is differentiated from the type of collapse or atelectasis which is secondary to pneumothorax, effusion or tumorous masses compressing and displacing alveolar tissue and bronchi as well. The collapse may be partial or total, depending on the amount of alveolar tissue involved, so that there may be a collapse of the entire lung,