or hairy mole.  It is of slow growth, may remain stationary for long periods, and has little or no tendency to become malignant.  It is usually subcutaneous, and is frequently situated on the head or neck in the distribution of the trigeminal or superficial cervical nerves.  There is no necessity for its removal, but this may be indicated because of disfigurement, especially on the face or scalp or because its bulk interferes with function.  When involving the ophthalmic division of the trigeminus, for example, it may cause enlargement of the upper lid and proptosis, with danger to the function of the globe.  The results of excision are usually satisfactory, even if the removal is not complete.

[Illustration:  FIG. 88.—­Multiple Neuro-fibromas of Skin (Molluscum fibrosum, or Recklinghausen’s disease).]

The cutaneous neuro-fibroma or molluscum fibrosum has been shown by Recklinghausen to be a soft fibroma related to the terminal filaments of one of the cutaneous nerves (Fig. 88).  The disease appears in the form of multiple, soft, projecting tumours, scattered all over the body, except the palms of the hands and soles of the feet.  The tumours are of all sizes, some being no larger than a pin’s head, whilst many are as big as a filbert and a few even larger.  Many are sessile and others are distinctly pedunculated, but all are covered with skin.  They are mobile, soft to the touch, and of the consistence of firm fat.  In exceptional cases one of the skin tumours may attain an enormous size and cause a hideous deformity, hanging down by its own weight in lobulated or folded masses (pachy-dermatocele).  The treatment consists in removing the larger swellings.  In some cases molluscum fibrosum is associated with pigmentation of the skin and with multiple tumours of the nerve-trunks.  The small multiple tumours rarely call for interference.

[Illustration:  FIG. 89.—­Elephantiasis Neuromatosa in a woman aet. 28]

Elephantiasis neuromatosa is the name applied by Virchow to a condition in which a limb is swollen and misshapen as a result of the extension of a neuro-fibromatosis to the skin and subcutaneous cellular tissue of the extremity as a whole (Fig. 89).  It usually begins in early life without apparent cause, and it may be associated with multiple tumours of the nerve-trunks.  The inconvenience caused by the bulk and weight of the limb may justify its removal.

SURGERY OF THE INDIVIDUAL NERVES[6]

[6] We desire here to acknowledge our indebtedness to Mr. James Sherren’s work on Injuries of Nerves and their Treatment.

#The Brachial Plexus.#—­Lesions of the brachial plexus may be divided into those above the clavicle and those below that bone.