This monograph deals with the clinical aspects of pneumococcic pleuritis of various types in infants. The first chapter covers the history of the development of the scientific knowledge of pleurisy. The etiology of pleurisy is discussed in relation to the bacteriology of the pneumococcus, portals of entry, time of appearance, frequency and influence of age and season. The pathologic anatomy is thoroughly discussed. About two thirds of the treatise is devoted to the symptoms, complications, diagnosis, prognosis and treatment of pneumococcic pleuritis. There are twenty-seven reproductions of illustrative roentgenograms. The emphasis throughout is on the practical and clinical aspects, which are presented in great detail.