#Tuberculosis of the Skin.#—­Interest attaches chiefly to the primary forms of tuberculosis of the skin in which the bacilli penetrate from without—­inoculation tubercle and lupus.

#Inoculation Tubercle.#—­The appearances vary with the conditions under which the inoculation takes place.  As observed on the fingers of adults, the affection takes the form of an indolent painless swelling, the epidermis being red and glazed, or warty, and irregularly fissured.  Sometimes the epidermis gives way, forming an ulcer with flabby granulations.  The infection rarely spreads to the lymphatics, but we have seen inoculation tubercle of the index-finger followed by a large cold abscess on the median side of the upper arm and by a huge mass of breaking down glands in the axilla.

In children who run about barefooted in towns, tubercle may be inoculated into wounds in the sole or about the toes, and although the local appearances may not be characteristic, the nature of the infection is revealed by its tendency to spread up the limb along the lymph vessels, giving rise to abscesses and fungating ulcers in relation to the femoral glands.

#Tuberculous Lupus.#—­This is an extremely chronic affection of the skin.  It rarely extends to the lymph glands, and of all tuberculous lesions is the least dangerous to life.  The commonest form of lupus—­lupus vulgaris—­usually commences in childhood or youth, and is most often met with on the nose or cheek.  The early and typical appearance is that of brownish-yellow or pink nodules in the skin, about the size of hemp seed.  Healing frequently occurs in the centre of the affected area while the disease continues to extend at the margin.

When there is actual destruction of tissue and ulceration—­the so-called “lupus excedens” or “ulcerans”—­healing is attended with cicatricial contraction, which may cause unsightly deformity.  When the cheek is affected, the lower eyelid may be drawn down and everted; when the lips are affected, the mouth may be distorted or seriously diminished in size.  When the nose is attacked, both the skin and mucous surfaces are usually involved, and the nasal orifices may be narrowed or even obliterated; sometimes the soft parts, including the cartilages, are destroyed, leaving only the bones covered by tightly stretched scar tissue.

The disease progresses slowly, healing in some places and spreading at others.  The patient complains of a burning sensation, but little of pain, and is chiefly concerned about the disfigurement.  Nothing is more characteristic of lupus than the appearance of fresh nodules in parts which have already healed.  In the course of years large tracts of the face and neck may become affected.  From the lips it may spread to the gum and palate, giving to the mucous membrane the appearance of a raised, bright-red, papillary or villous surface.  When the disease affects the gums, the teeth may become loose and fall out.