mb, but these phenomena are evanescent. _Injuries
to the great sciatic nerve_ are rare except in war. Partial division is
more common than complete, and it is noteworthy that the fibres destined
for the peroneal nerve are more often and more severely injured than
those for the tibial (internal popliteal). After complete division, all
the muscles of the leg are paralysed; if the section is in the upper
part of the thigh, the hamstrings are also paralysed. The limb is at
first quite powerless, but the patient usually recovers sufficiently to
be able to walk with a little support, and although the hamstrings are
paralysed the knee can be flexed by the sartorius and gracilis. The
chief feature is drop-foot. There is also loss of sensation below the
knee except along the course of the long saphenous nerve on the medial
side of the leg and foot. Sensibility to deep touch is only lost over a
comparatively small area on the dorsum of the foot.

#The Common Peroneal (external popliteal) nerve# is exposed to injury
where it winds round the neck of the fibula, because it is superficial
and lies against the unyielding bone. It may be compressed by a
tourniquet, or it may be bruised or torn in fractures of the upper end
of the bone. It has been divided in accidental wounds,--by a scythe, for
example,--in incising for cellulitis, and in performing subcutaneous
tenotomy of the biceps tendon. Cases have been observed of paralysis of
the nerve as a result of prolonged acute flexion of the knee in certain
occupations.

When the nerve is divided, the most obvious result is "drop-foot"; the
patient is unable to dorsiflex the foot and cannot lift his toes off the
ground, so that in walking he is obliged to jerk the foot forwards and
laterally. The loss of sensibility depends upon whether the nerve is
divided above or below the origin of the large cutaneous branch which
comes off just before it passes round the neck of the fibula. In course
of time the foot becomes inverted and the toes are pointed--pes
equino-varus--and trophic sores are liable to form.

#The Tibial (internal popliteal) nerve# is rarely injured.

#The Cranial nerves# are considered with affections of the head and neck
(Vol. II.).

NEURALGIA

The term neuralgia is applied clinically to any pain which follows the
course of a nerve, and is not referable to any discoverable cause. It
should not be applied to pain which results from pressure on a nerve by
a tumour, a ma