going on." This papular eruption may persist during the entire attack, or it may appear at any time during the course of the disease. When extensive and occurring late, it indicates a protracted attack.
The papule, having arrived at this stage, may either cease to grow, the apex becoming depressed, cupped, and lined with the yellow cheesy material alluded to; or it may go on, increasing in size, to the formation of the typical yaw. In the latter case the lesion gradually grows into a rounded excrescence, the yellow material at the top widening out so as to form a complete cap encrusting the little tumour. The yaw so formed may be no larger than a split pea; or it may attain the breadth of a crown-piece. The smaller tumours are hemispherical; the larger are more flattened or even depressed at the centre, possessing everted, somewhat overhanging, rounded edges. Occasionally, though rarely, a big yaw may include an area of sound skin. Several yaws may coalesce, and together cover a large and irregular surface, as an entire cheek, a popliteal space, or the dorsum of a foot. In the case of these large yaws, the surface of the growth is apt to be irregular and fissured. The neighbourhood of the mouth and anus are favourite sites for coalescent yaws; in such situations the moisture of the parts softens and removes the crust wholly or in part, so that the surface, in addition to being fissured, may be more or less bare, sodden, and fungoid.
The crust which caps and encloses an uninjured yaw is yellowish, granular, blotched with blood-stains and encrusted dirt. At first the crust is somewhat moist, but gradually it becomes dry, brown, and even black. The crusts are firmly adherent, requiring some force to remove them; a proceeding which, though painless, may entail a little oozing of blood. Deprived of its crust the little swelling is seen to be red in colour, and generally smooth and rounded on the surface. According to size, it stands out any thing from ⅛ to 6/8 in. above the surrounding healthy skin. Immediately after removal of the crust the exposed surface begins to pour out a pale, yellowish-
