SEROUS AND SERO-FIBRINOUS EXUDA nox.—In many cases besides the fibrin there is a tangible quantity of serous exudation containing fibrinous shreds. The fluid varies in quantity from a few drachms to an amount sufficient to enor mously distend the chest. Unless cir cumscribed by adhesions the fluid col lects at the lower and back part of the pleural cavity, allowing the lung in this situation to collapse by relieving it of the suction-action of the chest, to the extent of the bulk of the fluid. The fluid is yellowish, with a faintly-green tint, alkaline, and usually highly albu minous. Besides containing large cells from the proliferating endothelium, and a varying number of red blood-corpus cles, the fluid also contains leucocytes in various stages of transformation into pus. The pus-cells usually render the fluid somewhat cloudy and may be so abundant as to convert it into a sero purulent exudation. The amount of fibrin varies: in some cases it forms only a thin layer on the pleura; in others, be sides a thick creamy layer, it forms whitish, curdy masses in the lower part of the fluid.
If the effusion fills the pleural sac the lung will be compressed into a dark air less and even bloodless mass at its root and soon become carnified. In such cases the mediastinum and the heart and large vessels are displaced en nzasse to the opposite side. In left-sided effusions the cardiac impulse may appear near the right nipple and is caused by the impact, not of the apex, but probably of the right auricle and base of the right ventricle.
There is probably no rotation of the heart even in the most extensive cases, nor any kinking of the inferior vena cava. (Osler.) Series of 20 cases of primary pleurisy in which the leueocytes were counted daily from entrance to discharge or re covery. Their number exceeded 10,000, the normal limit, in only 13 of 224 counts. Nine of these occurred in one case with a secondary pneumococcic in fection. Nine of the eases were certainly tubercular, the others probably so. In the cases certainly tubercular the count never exceeded 10,000. There was no evi dent relation between the duration of the disease or the temperature and the num ber of white cells. Blood and micro scopical amounts of pus in the fluid did not affect their number. There was no apparent relation between the amount or progress of the fluid and the leucocyte count.
Serous pleurisy is only exceptionally accompanied by an increase in the num ber of white corpuscles, and then inter mittently. The white count is of value in two ways in the diagnosis of serous . pleurisy. If the physical signs are ful, and there is no leucocytosis, the eon dition is almost certainly not pneumonia or empyema, but serous pleurisy. If there is a serous pleurisy and a continu ous leucocytosis, some complication is present. H. L. Morse (Boston Med. and Surg. Jour., Dee. 13, 1900).