The foregoing case is particularly noteworthy because aspiration failed repeatedly to yield more than a few cubic centimeters of fluid, doubtless because the voluminous masses of fibrin present in the cavity prevented escape of fluid. Aspiration was attempted shortly before death, but only 4 c. c. of fluid were obtained; nevertheless, at autopsy the right pleural cavity contained 2,350 c.c. of exudate. Another factor of much importance in relation to treatment is the encapsulation of 450 c.c. of purulent fluid between the inner surface of the right lung and the pericardium. It is possible that free drainage might have emptied the main cavity and perhaps even freed the encapsulated fluid. =Pericarditis.=—Among 241 autopsies on individuals with pneumonia following influenza, pericarditis occurred 23 times; these lesions were classified as follows: Serous pericarditis, 1; serofibrinous pericarditis, 9; seropurulent pericarditis, 1; fibrinopurulent pericarditis, 10; purulent pericarditis, 2. It is noteworthy that in 12 of 23 instances of pericarditis the lesion was associated with S. hemolyticus infection of the lung and whenever in these instances cultures were made (Autopsies 434, 485, 499 and 504) hemolytic streptococci were obtained from the pericardial exudate in pure culture. The tendency of interstitial suppurative pneumonia to produce pericarditis is especially evident. Among 21 instances of interstitial suppurative pneumonia pericarditis occurred 6 times (28.6 per cent); among 39 instances of suppurative pneumonia with abscess formation, pericarditis occurred twice (5.1 per cent); whereas among all other autopsies, namely, 181, the lesion occurred 15 times (8.3 per cent). Pericarditis occurred in association with pneumonia referable to Pneumococcus I, once, (Pneumococcus I isolated from the pericardium); to Pneumococcus II, once; to atypical Pneumococcus II, 5 times (twice isolated from the pericardium); and to Pneumococcus IV, twice (once isolated from the pericardium). =Peritonitis.=—Purulent peritonitis occurred only twice, in both instances in association with pneumonia caused by hemolytic streptococci. Purulent peritonitis was part of a general serositis involving both pleural cavities, pericardium and peritoneum in 2 noteworthy instances: =Autopsy 465.=—J. K., white, aged twenty-two, farmer from Oklahoma, had been in military service one month. He was admitted to the hospital with influenza, sore throat and bronchitis twenty-four days before his death. Signs of pneumonia were recognized thirteen days later and at the same time there was otitis media on the right side. Empyema and pericarditis were found three days before death and two days later 1000 c.c. of cloudy fluid were withdrawn from the chest.