_In the male_, the primary lesion specially affects certain _situations_, and the appearances vary with these: (1) On the inner aspect of the prepuce, and in the fold between the prepuce and the glans; in the latter situation the induration imparts a "collar-like" rigidity to the prepuce, which is most apparent when it is rolled back over the corona. (2) At the orifice of the prepuce the primary lesion assumes the form of multiple linear ulcers or fissures, and as each of these is attended with infiltration, the prepuce cannot be pulled back--a condition known as _syphilitic phimosis_. (3) On the glans penis the infiltration may be so superficial that it resembles a layer of parchment, but if it invades the cavernous tissue there is a dense mass of induration. (4) On the external aspect of the prepuce or on the skin of the penis itself. (5) At either end of the torn frænum, in the form of a diamond-shaped ulcer raised above the surroundings. (6) In relation to the meatus and canal of the urethra, in either of which situations the swelling and induration may lead to narrowing of the urethra, so that the urine is passed with pain and difficulty and in a minute stream; stricture results only in the exceptional cases in which the chancre has ulcerated and caused destruction of tissue. A chancre within the orifice of the urethra is rare, and, being concealed from view, it can only be recognised by the discharge from the meatus and by the induration felt between the finger and thumb on palpating the urethra. _In the female_, the primary lesion is not so typical or so easily recognised as in men; it is usually met with on the labia; the induration is rarely characteristic and does not last so long. The primary lesion may take the form of condylomata. Indurated œdema, with brownish-red or livid discoloration of one or both labia, is diagnostic of syphilis. The hard chancre is usually solitary, but sometimes there are two or more; when there are several, they are individually smaller than the solitary chancre. It is the exception for a hard chancre to leave a visible scar, hence, in examining patients with a doubtful history of syphilis, little reliance can be placed on the presence or absence of a scar on the genitals. When the primary lesion has taken the form of an open ulcer with purulent discharge, or has sloughed, there is a permanent scar.