It is an established fact that at least 70 per cent. of all cases of the serofibrinous type of pleurisy in adults are of tuberculous origin, the figures of various observers varying from 15 per cent. to 82.6 per cent.
I need not here review the literature or quote statistics which establish this fact, since this has only recently been done by Lord1 and in 1908 by S. Goodall,2 but I shall briefly discuss the methods by which we may ascertain the true etiology of pleuritic effusions.
We shall here exclude the transudates due to circulatory disturbance, kidney affections, cancer, or injuries to the pleura and confine our study to the forms which are associated with or follow inflammatory diseases of the lungs, pleura or neighboring organs.
Dealing, then, with only inflammatory types of effusions, our first step is to determine what disease is its causative factor. Is it