Affections of the Skin are among the most constant manifestations.  An evanescent macular rash, not unlike that of measles—­roseola—­is the first to appear, usually in from six to eight weeks from the date of infection; it is widely diffused over the trunk, and the original dull rose-colour soon fades, leaving brownish stains, which in time disappear.  It is usually followed by a papular eruption, the individual papules being raised above the surface of the skin, smooth or scaly, and as they are due to infiltration of the skin they are more persistent than the roseoles.  They vary in size and distribution, being sometimes small, hard, polished, and closely aggregated like lichen, sometimes as large as a shilling-piece, with an accumulation of scales on the surface like that seen in psoriasis.  The co-existence of scaly papules and faded roseoles is very suggestive of syphilis.

Other types of eruption are less common, and are met with from the third month onwards.  A pustular eruption, not unlike that of acne, is sometimes a prominent feature, but is not characteristic of syphilis unless it affects the scalp and forehead and is associated with the remains of the papular eruption.  The term ecthyma is applied when the pustules are of large size, and, after breaking on the surface, give rise to superficial ulcers; the discharge from the ulcer often dries up and forms a scab or crust which is continually added to from below as the ulcer extends in area and depth.  The term rupia is applied when the crusts are prominent, dark in colour, and conical in shape, roughly resembling the shell of a limpet.  If the crust is detached, a sharply defined ulcer is exposed, and when this heals it leaves a scar which is usually circular, thin, white, shining like satin, and the surrounding skin is darkly pigmented; in the case of deep ulcers, the scar is depressed and adherent (Fig. 39).

[Illustration:  FIG. 39.—­Syphilitic Rupia, showing the limpet-shaped crusts or scabs.]

In the later stages there may occur a form of creeping or spreading ulceration of the skin of the face, groin, or scrotum, healing at one edge and spreading at another like tuberculous lupus, but distinguished from this by its more rapid progress and by the pigmentation of the scar.

Condylomata are more characteristic of syphilis than any other type of skin lesion.  They are papules occurring on those parts of the body where the skin is habitually moist, and especially where two skin surfaces are in contact.  They are chiefly met with on the external genitals, especially in women, around the anus, beneath large pendulous mammae, between the toes, and at the angles of the mouth, and in these situations their development is greatly favoured by neglect of cleanliness.  They present the appearance of well-defined circular or ovoid areas in which the skin is thickened and raised above the surface; they