Microscopic examination shows that bronchi, bronchioles, alveolar ducts and the greater part of the infundibula are filled with polynuclear leucocytes, whereas the alveoli surrounding these structures contain fibrin. The walls of the small bronchi are thickened and contain mononuclear cells; the adjacent alveolar walls are similarly infiltrated and thickened and the fibrin within them is undergoing organization, being invaded by plasma cells, fibroblasts and newly formed blood vessels. In some sections interstitial septa are distended by edema and contain fibrin in abundance; in places the tissue contains polynuclear leucocytes closely packed together. There are lymphatics greatly distended by polynuclear leucocytes with some fibrin, lymphocytes and red blood corpuscles. =Autopsy 428.=—D. B., white, aged twenty-five, a farmer from Oklahoma, had been in military service three weeks. Onset of illness was on September 21, twenty-five days before death, with fever, cough and mucopurulent expectoration. The patient was admitted with the diagnosis of acute bilateral bronchitis. Four days later bronchopneumonia was recognized, and subsequently there was otitis media and empyema; 600 c.c. of thin, purulent fluid were aspirated from the right chest three days before death. =Anatomic Diagnosis.=—Unresolved bronchopneumonia; suppuration of interstitial tissue of upper right and lower left lobes; purulent bronchitis; fibrinopurulent pleurisy; thoracotomy wound at the base of the right chest; collapse of both lungs; serofibrinous pericarditis. The left pleural cavity contains 550 c.c. of turbid seropurulent fluid in which are numerous flakes of soft fibrin. The right pleural cavity contains 150 c.c. of similar fluid. The mediastinum is edematous. The pericardial cavity contains 50 c.c. of yellow fluid. The right lung is moderately collapsed. In the upper and lower lobes are small patches of red, lobular consolidation. The upper third of the upper lobe is laxly consolidated and near its inner surface the interstitial septa are thickened to from 1 to 1.5 mm. in width, and at intervals occur bead-like swellings from which creamy purulent fluid exudes upon the cut surface. In the left lung small patches of gray consolidation occur throughout the lower lobe and here the interstitial septa are thickened, beaded and contain purulent fluid. Bacteriologic examination shows that the blood contains S. hemolyticus; from the right lung and from the right main bronchus hemolytic streptococci and B. influenzæ are grown.