This name is applied to small multiple growths of the skin, occurring chiefly on the face and showing a preference for the eyelids, but sometimes extending so as to be almost universal over the body. The individual nodules have been compared to pearl buttons, which they resemble in their circular shape and central depression, but they are usually pink in colour. There is considerable elevation of the little growth, and. although generally sessile, it sometimes becomes pedunculated and may even drop off.

The little nodule (see Fig. 483) consists essentially of new- formed epithelium, in the cells of which the peculiar bodies form which many regard as parasitic protozoa (see under Cancer). The whole tumour looks like an enlarged and altered sebaceous gland with its lobules and central duct, but the observations of Virchow, Thin, and others render it very doubtful if the lesions have this origin. Thin believes that the infective agent gets in by the hair follicles and stimulates the Mal-pighian layer of the epidermis to new-formation. The sebaceous glands are really pushed aside by the growing tumour.

Molluscum contagiosum. It forms a flat elevation as shown by the position of the epidermic surface on either side, x 20.

Fig. 483. - Molluscum contagiosum. It forms a flat elevation as shown by the position of the epidermic surface on either side, x 20.

The disease depends on some virus, and, as the name implies, it is contagious. It generally occurs in groups in the same person, as if spreading, and several members of the same family, or several persons living together, are usually affected simultaneously. It is usually seen in children, but occurs also in adults.