The change into the moist papule (also called _mucous patch, flat condyloma_) is not uncommon where opposing surfaces and natural folds of skin are subjected to more or less contact, as about the anus, the scroto-femoral regions, umbilicus, axillae and beneath the mammae. The dry, flat papules gradually become moist and covered with a grayish, sticky, mucoid secretion; several may coalesce and form large, flat patches. They may so remain, or they may become hypertrophic, warty or papillomatous, with more or less crust formation (_vegetating syphiloderm_). [Illustration: Fig. 54. Annular Syphiloderm. (_After I.E. Atkinson._)] #Describe the squamous papule of syphilis.# This tendency of the large-papular eruption to become scaly, when exhibited, is more or less common to all papules, and constitutes the _squamous_ or _papulo-squamous syphiloderm_ (improperly called _psoriasis syphilitica_). The papules become somewhat flattened and are covered with dry, grayish or dirty-gray, somewhat adherent scales. The scaling, as compared to that of psoriasis, is, as a rule, relatively slight. The eruption may be general, as usually the case in the earlier months of the disease, or it may appear as a relapse or a later manifestation, and be limited in extent. As a limited eruption it is most frequently seen on the palms and soles--the _palmar and plantar syphiloderm_. Occurring on these parts it is often rebellious to treatment. [Illustration: Maculo-papular syphiloderm.] #How are you to distinguish the papulo-squamous syphiloderm from psoriasis?# In psoriasis the eruption is more inflammatory, and usually bright red; the scales whitish or pearl-colored and, as a rule, abundant. It is generally seen in greater profusion upon certain parts, as, for instance, the extensor surfaces, especially of the elbows and knees. It is not infrequently itchy, and, moreover, presents a different history. In the syphilitic eruption some of the papules almost invariably remain perfectly free from any tendency to scale formation; there is distinct deposit or infiltration, and the lesions are of a dark, sluggish red or ham tint; and, moreover, concomitant symptoms of syphilis are usually present. #Describe the annular eruption of syphilis.# The _annular syphiloderm_ (_circinate syphiloderm_) is observed usually in association with the large-papular eruption, and consists of several or more variously sized, ring-like lesions, with a distinctly elevated solid ridge or wall peripherally and a more or less flattened centre. It is commonly seen about the mouth, forehead and neck. The lesion appears to have its origin from an ordinary, usually scaleless or slightly scaly, large papule, the central portion of which has been incompletely formed or has become sunken and flattened. The manifestation is rare, and is seen most frequently in the negro. #What several varieties of the pustular syphiloderm are met with?#