situated on the sole of the foot or in the matrix of the nail of the great toe, the femoral and inguinal glands become enlarged in succession, forming tumours much larger than the primary growth.  Sometimes the dissemination involves the lymph vessels of the limb, forming a series of indurated pigmented cords and nodules (Fig. 104).  Lastly, the dissemination may be universal throughout the body, and this usually occurs at a comparatively early stage.  The secondary growths are deeply pigmented, being usually of a coal-black colour, and melanin pigment may be present in the urine.  When recurrence takes place in or near the scar left by the operation, the cancer nodules are not necessarily pigmented.

[Illustration:  FIG. 104.—­Diffuse Melanotic Cancer of Lymphatics of Skin secondary to a Growth in the Sole of the Foot.]

To extirpate the disease it is necessary to excise the tumour, with a zone of healthy skin around it and a somewhat large zone of the underlying subcutaneous tissue and deep fascia.  Hogarth Pringle recommends that a broad strip of subcutaneous fascia up to and including the nearest anatomical group of glands should be removed with the tumour in one continuous piece.

#Secondary Cancer of the Skin.#—­Cancer may spread to the skin from a subjacent growth by direct continuity or by way of the lymphatics.  Both of these processes are so well illustrated in cases of mammary cancer that they will be described in relation to that disease.

#Sarcoma# of various types is met with in the skin.  The fibroma, after excision, may recur as a fibro-sarcoma.  The alveolar sarcoma commences as a hard lump and increases in size until the epidermis gives way and an ulcer is formed.

[Illustration:  FIG. 105.—­Melanotic Cancer of Forehead with Metastases in Lymph Vessels and Glands.

(Mr. D. P. D. Wilkie’s case.)]

A number of fresh tumours may spring up around the original growth.  Sometimes the primary growth appears in the form of multiple nodules which tend to become confluent.  Excision, unless performed early, is of little avail, and in any case should be followed up by exposure to radium.

AFFECTIONS OF CICATRICES

A cicatrix or scar consists of closely packed bundles of white fibres covered by epidermis; the skin glands and hair follicles are usually absent.  The size, shape, and level of the cicatrix depend upon the conditions which preceded healing.

A healthy scar, when recently formed, has a smooth, glossy surface of a pinkish colour, which tends to become whiter as a result of obliteration of the blood vessels concerned in its formation.

Weak Scars.—­A scar is said to be weak when it readily breaks down as a result of irritation or pressure.  The scars resulting from severe burns and those over amputation stumps are especially liable to break down from trivial causes.  The treatment is to excise the weak portion of the scar and bring the edges of the gap together.