A. =Dry Papule.=--The _dry papule_ commences as a small rounded area of redness, becoming infiltrated and rising above the surface, gradually developing into a nodule the size of a pea or larger, over which the superficial skin seems to be thickened. Should the summit of this nodule become abraded there will escape a serous fluid, which dries and forms a thin scab. This papule may disappear more slowly than it came, or may become more infiltrated, while its surface breaks down into an ulcer, whose area will be dropped a little below that of the surrounding tissue. In this case the induration is produced almost entirely by new round-cell infiltration, as in the other varieties; when it ulcerates these cells are the ones mainly to suffer, so that there is not much destruction of the original elements, and but little scar remains. B. =Superficial Erosion.=--The superficial erosion is the most common of the primitive sores, but is not often seen so early as to have its first appearance noted. It begins as a well-defined, dark-red area, which loses its epithelium and exposes a raw surface, with a trifling depression whose edges are usually on a level with the surrounding skin, while in the previous case the edges are generally characterized by an elevated margin. The base of this sore is also indurated, and partakes usually of the parchment-like character already described. C. =Hunterian Chancre.=--The Hunterian chancre, so named after John Hunter’s description of it, is the most distinct and typical of these primary lesions. It begins as a papule, with some erosion, increasing slowly in size, sharply outlined, with a somewhat flat top. As it grows larger it increases in firmness until its base is extremely dense. In color it is greenish or bluish red, and this color appearance is more distinctive than in the other forms. In from one to three weeks its surface epithelium is usually loosened by maceration, and serous discharge is the consequence, or else it becomes covered with a grayish exudate, which, by its location, is rarely allowed to form a scab. The centre of the ulcer becomes deeper, its edges more elevated, and in typical cases a minute crater is formed by a characteristic destructive process. While the Hunterian chancre tends in ordinary cases to slowly disappear of itself, this involution can be materially hastened by local and constitutional treatment, and usually heals, when properly treated, with but slight local evidence of its previous existence.