This is the common wart, occurring mostly upon the hands. It is rounded, elevated, circumscribed, hard and horny, with a broad base, and usually the size of a pea. At first it is smooth and covered with slightly thickened epidermis, but later this disappears to some extent, the hypertrophied papillae, appearing as minute elevations, making up the growth. One, several or more may be present. #Describe verruca plana.# This is the so-called flat wart, and occurs commonly upon the back, especially in elderly people (_verruca senilis_, _keratosis pigmentosa_). It is, as a rule, but slightly elevated, is usually dark in color, and of the size of a pea or finger-nail. #Describe verruca plana juvenilis.# The warts are mostly pin-head in size, flat, but slightly elevated, rounded, irregular or square-shaped, and of a light yellowish-brown color. They bear resemblance to lichen planus papules. They are apt to be numerous, often becoming aggregated or fused, and occur usually in young children, and, as a rule, on the face and hands. #Describe verruca filiformis.# This is a thread-like growth about an eighth or fourth of an inch long, and occurring commonly about the face, eyelids and neck. It is usually soft to the touch and flexible. #Describe verruca digitata.# This is a variety of wart, which, especially about the edges, is marked by digitations, extending nearly or quite down to the base. It is commonly seen upon the scalp. #Describe verruca acuminata.# This variety (_venereal wart_, _pointed wart_, _pointed condyloma_), usually occurs about the genitalia, especially upon the mucous and muco-cutaneous surfaces. It consists of one or more groups of acuminated, pinkish or reddish, raspberry-like elevations, and, according to the region, may be dry or moist; if the latter, the secretion, which is usually yellowish and puriform, from rapid decomposition, develops an offensive and penetrating odor. The formation may be the size of a small pea, or may attain the dimensions of a fist. #What is the cause of warts?# The etiology is not known. They are more common in adolescent and early adult life. Irritating secretions are thought to be causative in the acuminated variety. It is highly probable that a parasitic factor will finally be demonstrated. They are doubtless mildly contagious. [Illustration: Fig. 33. Verruca Acuminata--about the anus. (_After Ashton._)] #State the pathology of warts.# A wart consists of both epidermic and papillary hypertrophy, the interior of the growth containing a vascular loop. In the acuminated variety there are marked papillary enlargement, excessive development of the mucous layer, and an abundant vascular supply. #Give the treatment of warts.#