A microscopic section through the abscess and its communication with the pleura shows that its cavity contains polynuclear leucocytes and the wall is formed by granulation tissue covered by fibrin. Some alveoli outside the abscess contain compact balls of fibrin containing a few fibroblasts; this fibrin stains deeply with hematoxylin as if it contained calcium. The surface of the lung is covered by fibrin in process of organization. In the foregoing instance a pulmonary abscess on the right side has ruptured into the pleura and, completely separated from the adjacent lung by a wall of newly formed tissue, is in process of healing. It shows that these pulmonary abscesses below the pleura may heal provided drainage is established by rupture into the pleural cavity and subsequent evacuation of pleural exudate. It is noteworthy that in this instance empyema extended from the right to the left pleural cavity, both S. hemolyticus and S. aureus were found at autopsy. The thoracotomy wound on the right side was closed at autopsy. Interstitial Suppurative Pneumonia A second type of suppurative pneumonia is characterized by acute inflammation of interstitial tissue between the secondary lobules of the lung and by acute lymphangitis; suppuration involves the interstitial septa and the walls of the lymphatics. The lesion is designated by Kaufmann,[82] Beitzke[83] and others acute interstitial pneumonia. _Pneumonia dissecans_ in which solution of interstitial tissue isolates sections of lung tissue is said to be a consequence of the lesion. Many text books of pathology, overlooking the occurrence of this lesion, limit the consideration of interstitial pneumonia to chronic processes in which the interlobular and interalveolar fibrous tissue is increased.