Since William Pasteur1first described pulmonary atelectasis following diphtheria and then discussed its occurrence following surgical procedures2massive collapse of the lung has been frequently recognized by the medical practitioner. The causes, symptoms and signs of this condition are well known and adequately described in the modern textbooks. The prognosis as to life when the condition is uncomplicated is usually excellent, although death may occur in debilitated subjects if collapse occurs in more than one lobe or bilaterally.3The greatest danger in pulmonary atelectasis is the secondary development of pneumonia. Since pneumonia in itself is a serious disease, it becomes important either to prevent pulmonary atelectasis or to relieve it as soon as possible when it does occur. In this brief report we shall confine ourselves to the therapy of the condition after it has occurred and make no mention of prophylaxis. The methods of therapy usually