paralysis of the coraco-brachialis, biceps, and part of the
brachialis, but no movements are abolished, the forearm being flexed, in
the pronated position, by the brachio-radialis and long radial extensor
of the wrist; in the supinated position, by that portion of the
brachialis supplied by the radial nerve. Supination is feebly performed
by the supinator muscle. Protopathic and epicritic sensibility are lost
over the radial side of the forearm.

#Radial (Musculo-Spiral) Nerve.#--From its anatomical relationships this
trunk is more exposed to injury than any other nerve in the body. It is
frequently compressed against the humerus in sleeping with the arm
resting on the back of a chair, especially in the deep sleep of
alcoholic intoxication (drunkard's palsy). It may be pressed upon by a
crutch in the axilla, by the dislocated head of the humerus, or by
violent compression of the arm, as when an elastic tourniquet is applied
too tightly. The most serious and permanent injuries of this nerve are
associated with fractures of the humerus, especially those from direct
violence attended with comminution of the bone. The nerve may be crushed
or torn by one of the fragments at the time of the injury, or at a later
period may be compressed by callus.

_Clinical Features._--Immediately after the injury it is impossible to
tell whether the nerve is torn across or merely compressed. The patient
may complain of numbness and tingling in the distribution of the
superficial branch of the nerve, but it is a striking fact, that so long
as the nerve is divided below the level at which it gives off the dorsal
cutaneous nerve of the forearm (external cutaneous branch), there is no
loss of sensation. When it is divided above the origin of the dorsal
cutaneous branch, or when the dorsal branch of the musculo-cutaneous
nerve is also divided, there is a loss of sensibility on the dorsum
of the hand.

The motor symptoms predominate, the muscles affected being the extensors
of the wrist and fingers, and the supinators. There is a characteristic
"drop-wrist"; the wrist is flexed and pronated, and the patient is
unable to dorsiflex the wrist or fingers (Fig. 90). If the hand and
proximal phalanges are supported, the second and third phalanges may be
partly extended by the interossei and lumbricals. There is also
considerable impairment of power in the muscles which antagonise those
that are paralysed, so that the grasp of the hand is feeble, and