I do not find the literature on this subject very extensive. While attending lectures in Paris I observed many interesting cases in the Hopitaux Des Enfants Trouves, which I had the privilege of visiting daily for a month in company with the physician in charge. Since then it has been my fortune to encounter a number of cases in my own practice. Last winter, especially, pleurisy seemed very prevalent, accompanying as well as following the different forms of acute pneumonia. We seldom find pleurisy a primary disease. In my experience effusions of the right side predominate over the left. Pleuritic exudate, either serous or purulent, is common in infancy and childhood; more particularly the latter, especially before the fifth year of life. As the chest wall at this age is more resilient than in the adult, large exudates are better borne, producing fewer pressure symptoms. ETIOLOGY. The etiology is at