#Secondary Tumours.#—­Next to tuberculosis, secondary cancer is the most common disease of lymph glands.  In the neck it is met with in association with epithelioma of the lip, tongue, or fauces.  The glands form tumours of variable size, and are often larger than the primary growth, the characters of which they reproduce.  The glands are at first movable, but soon become fixed both to each other and to their surroundings; when fixed to the mandible they form a swelling of bone-like hardness; in time they soften, liquefy, and burst through the skin, forming foul, fungating ulcers.  A similar condition is met with in the groin from epithelioma of the penis, scrotum, or vulva.  In cancer of the breast, the infection of the axillary glands is an important complication.

In pigmented or melanotic cancers of the skin, the glands are early infected and increase rapidly, so that, when the primary growth is still of small size—­as, for example, on the sole of the foot—­the femoral glands may already constitute large pigmented tumours.

[Illustration:  FIG. 83.—­Cancerous Glands in Neck secondary to Epithelioma of Lip.

(Mr. G. L. Chiene’s case.)]

The implication of the glands in other forms of cancer will be considered with regional surgery.

Secondary sarcoma is seldom met with in the lymph glands except when the primary growth is a lympho-sarcoma and is situated in the tonsil, thyreoid, or testicle.

CHAPTER XVI

THE NERVES

Anatomy—­INJURIES OF NERVES:  Changes in nerves after division;
    Repair and its modifications; Clinical features; Primary and
    secondary suture—­SUBCUTANEOUS INJURIES OF
    NERVES—­DISEASES:  Neuritis; Tumours—­Surgery of
    the individual nerves:  Brachial neuralgia; Sciatica;
    Trigeminal neuralgia.

#Anatomy.#—­A nerve-trunk is made up of a variable number of bundles of nerve fibres surrounded and supported by a framework of connective tissue.  The nerve fibres are chiefly of the medullated type, and they run without interruption from a nerve cell or neuron in the brain or spinal medulla to their peripheral terminations in muscle, skin, and secretory glands.

Each nerve fibre consists of a number of nerve fibrils collected into a central bundle—­the axis cylinder—­which is surrounded by an envelope, the neurolemma or sheath of Schwann.  Between the neurolemma and the axis cylinder is the medullated sheath, composed of a fatty substance known as myelin.  This medullated sheath is interrupted at the nodes of Ranvier, and in each internode is a nucleus lying between the myelin and the neurolemma.  The axis cylinder is the essential conducting structure of the nerve, while the neurolemma and the myelin act as insulating agents.  The axis cylinder depends for its nutrition on the central neuron with which it is connected, and from which it originally developed, and it degenerates if it is separated from its neuron.