urface, but it also tends to
invade the cranial cavity, and may thus assume the shape of a
dumb-bell. Its growth is usually rapid, and results in the formation
of a diffuse soft swelling, which sometimes pulsates, and sooner or
later fungates through the skin. On account of its rapid growth the
tumour is liable to be mistaken for an abscess, and in some cases the
nature of the disease is only discovered after making an exploratory
incision, and finding that the finger passes through a softened area
in the bone.

When the cranial cavity is encroached upon, signs of compression
ensue. After the tumour has fungated, infective complications within
the skull are liable to develop. In all cases the prognosis is
extremely unfavourable.

If diagnosed sufficiently early, an attempt may be made to remove the
tumour, but often the operation has to be abandoned, either on account
of the haemorrhage which attends it, or because of the extent of the
disease.

The bones of the skull may become the seat of _secondary growths_ by
the direct spread of cancer from the soft parts, _e.g._ rodent cancer
(Fig. 204), or by metastasis of cancer or sarcoma from distant parts
of the body, or of thyreoid tumours. Metastatic cancer would appear to
be conveyed by the blood stream; it may occur in a diffuse
form--cancerous osteomalacia--softening the calvaria so that at the
post-mortem examination it may be removed with the knife instead of
the saw; or it occurs in a discrete or scattered form, and then the
macerated skull presents a number of circular and oval perforations.

[Illustration: FIG. 204.--Destruction of Bones of Left Orbit, caused
by Rodent Cancer. The patient died of septic meningitis.

(Mr. D. M. Greig's case.)]

CHAPTER XVI

THE VERTEBRAL COLUMN AND SPINAL CORD

Surgical Anatomy--Injuries of the spinal cord: _Concussion_;
_Traumatic haematorrachis_; _Traumatic haematomyelia_; _Total
transverse lesions at different levels_; _Partial lesions_;
"_Railway spine_"--Injuries of the vertebral column: _Sprain_;
_Isolated dislocation of articular processes_; _Isolated fracture
of arches and spinous processes_; _Compression fracture of
bodies_--Traumatic spondylitis--Fracture-dislocation--Penetrating
wounds.

#Surgical Anatomy.#--The veretebral column is the central axis of the
skeleton, and affords a protecting casement for the spinal cord.

The spine is movable in all directions--flexion, exte