estoration of function is attained, or when thermalgic pain is
excessive.

#Subcutaneous Injuries of Nerves.#--Several varieties of subcutaneous
injuries of nerves are met with. One of the best known is the
compression paralysis of the nerves of the upper arm which results from
sleeping with the arm resting on the back of a chair or the edge of a
table--the so-called "drunkard's palsy"; and from the pressure of a
crutch in the axilla--"crutch paralysis." In some of these injuries,
notably "drunkard's palsy," the disability appears to be due not to
damage of the nerve, but to overstretching of the extensors of the wrist
and fingers (Jones). A similar form of paralysis is sometimes met with
from the pressure of a tourniquet, from tight bandages or splints, from
the pressure exerted by a dislocated bone or by excessive callus, and
from hyper-extension of the arm during anaesthesia.

In all these forms there is impaired sensation, rarely amounting to
anaesthesia, marked muscular wasting, and diminution or loss of voluntary
motor power, while--and this is a point of great importance--the normal
electrical reactions are preserved. There may also develop trophic
changes such as blisters, superficial ulcers, and clubbing of the tips
of the fingers. The prognosis is usually favourable, as recovery is the
rule within from one to three months. If, however, neuritis supervenes,
the electrical reactions are altered, the muscles degenerate, and
recovery may be retarded or may fail to take place.

Injuries which act abruptly or instantaneously are illustrated in the
crushing of a nerve by the sudden displacement of a sharp-edged fragment
of bone, as may occur in comminuted fractures of the humerus. The
symptoms include perversion or loss of sensation, motor paralysis, and
atrophy of muscles, which show the reaction of degeneration from the
eighth day onwards. The presence of the reaction of degeneration
influences both the prognosis and the treatment, for it implies a lesion
which is probably incapable of spontaneous recovery, and which can only
be remedied by operation.

The _treatment_ varies with the cause and nature of the lesion. When,
for example, a displaced bone or a mass of callus is pressing upon the
nerve, steps must be taken to relieve the pressure, by operation if
necessary. When there is reason to believe that the nerve is severely
crushed or torn across, it should be exposed by incision, and, after
removal of the da