The foregoing study has shown, on the one hand, that empyema is a frequent complication of streptococcus pneumonia and, on the other hand, that empyema following influenza with relatively few exceptions is caused by hemolytic streptococci. Empyema caused by this microorganism exhibits in some instances characters not seen with other varieties of pleural inflammation. The tissue between sternum and pericardium is often edematous and the adjacent fat has a firm brawny consistence. In some instances the exudate contains blood, and hemolysis has occurred so that the fluid has a diffuse red color. The occurrence of multiple pocketed collections of purulent fluid within the pleural cavity is peculiar to streptococcus empyema. These pockets have been found 6 times in association with abscess and 5 times with interstitial suppurative pneumonia. In the presence of an exudate within the pleural cavity, some part of the lung, usually the anterior surface behind the sternum and costal cartilages, is glued by fibrinous adhesions to the parietal pleura. Here occur pockets containing thin purulent fluid and softened fibrin or thicker creamy pus walled off by fibrin about the edges of the pocket. At the site of the lesion the lung, after it is separated from the chest wall, is marked by a shallow depression surrounded by the fibrin which has walled in the pocket. The little cavity thus formed, varying much in size, is usually oval, the long diameter being from 1 to 3 cm. These pleural pockets may occur over the external surface of the lung (Autopsies 452, 455, and 472) or between the internal surface and pericardium (Autopsy 452). Occasionally with partial fibrinous adhesion between the pleural surfaces there are both scattered pockets containing purulent fluid and a larger encapsulated collection of fluid; in Autopsy 455 the pleural surfaces were adherent and there was 100 c.c. of purulent fluid encapsulated in a space over the external surface of the lung, 12 × 8 cm. In Autopsy 452 the lower part of the pleural cavity was encapsulated and contained 650 c.c. of fluid. This tendency of empyema caused by S. hemolyticus to form encapsulated pockets is doubtless of considerable importance in the treatment of the condition. Stone, Bliss and Phillips[85] have described these encapsulated pockets as “subcostosternal pus pockets” and have maintained that they are formed about the sternal lymphatic nodes. We have found them so widely scattered that this relation seems improbable. =Pneumococcus Empyema.=—Empyema occurred in association with pneumonia referable to pneumococci 10 times, once with Pneumococcus II; 6 times with Pneumococcus atypical II; once with Pneumococcus III and twice with Pneumococcus IV. The lesion was seropurulent once; fibrinopurulent 8 times and purulent once. Fibrin in several instances was somewhat voluminous. In the following instance voluminous masses of fibrin had an important influence upon the attempted treatment.