=Autopsy 397.=—N. P., white, aged twenty-one, farmer, a native of Oklahoma, had been in military service twenty-one days. Illness began twenty-two days before death, the patient being admitted on the day following onset with influenza, pharyngitis and bronchitis. A diagnosis of lobar pneumonia was made fourteen days before death. The left pleural cavity was aspirated twelve days later and 800 c.c. of thick yellow pus were withdrawn. Hemolytic streptococci were found in the sputum five days before death. =Anatomic Diagnosis.=—Interstitial suppurative pneumonia in left upper lobe; acute bronchopneumonia with lobular consolidation in right upper lobe; localized purulent pleurisy on left side with compression and atelectasis of left lung; compensatory emphysema of right lung; purulent bronchitis; beginning serofibrinous pericarditis; chronic passive congestion of liver, spleen and kidneys. The right lung is very voluminous, free from coal pigment and bright pink save over lobular patches of consolidation which have a bluish red color; the bronchi contain mucopurulent material. The anterior surface of the left lung is bound to the chest wall by firm adhesions, but over the external and posterior surfaces of the lung there is a localized cavity containing 1,100 c.c. of turbid fluid. The left lung is collapsed and airless with deep fleshy red color. In the upper lobe there are scattered patches of consolidation 1.5 to 2.5 cm. across where the tissue is grayish red and coarsely granular. In the adjacent tissue interstitial septa are thickened to 1 or 2 mm. and are conspicuous as gray bands. Along their course occur bead-like swellings from which purulent fluid can be scraped. These septa at one point reach the anterior surface of the lung where the pleural cavity is in large part obliterated by adhesions; here there is an encapsulated pocket 4 x 1.5 cm. containing thick creamy pus. Bacteriologic examination of the blood shows the presence of hemolytic streptococci; cultures from the lungs contain hemolytic streptococci and B. influenzæ. Microscopic examination shows that interlobular septa are thickened and infiltrated with plasma cells in large number. Leucocytes in the center of much dilated lymphatics have undergone necrosis and have lost their nuclear stain. About the periphery of the lumen and evidently derived from the swollen endothelial cells which surround it, are numerous large mononuclear cells. They act as phagocytes and ingest polynuclear leucocytes. Multinucleated giant cells, derived from these cells, occur. In several places thrombosed lymphatics in process of organization occur; the lumen is filled with compact fibrin which is invaded by fibroblasts and newly formed capillaries.