of them, in relieving the spasm. In a case of spastic
contracture of the pronator muscles of the forearm, for example, an
incision is made along the line of the median nerve above the bend of
the elbow. At the lateral side of the median nerve, where it lies in
contact with the biceps muscle, is situated a well-defined and easily
isolated bundle of fibres which supplies the pronator teres, the flexor
carpi radialis, and the palmaris longus muscles. On incising the sheath
of the nerve this bundle can be readily dissected up and its identity
confirmed by stimulating it with a very weak galvanic current. An inch
or more of the bundle is then resected.

INJURIES OF NERVES

Nerves are liable to be cut or torn across, bruised, compressed,
stretched, or torn away from their connections with the spinal medulla.

#Complete Division of a Mixed Nerve.#--Complete division is a common
result of accidental wounds, especially above the wrist, where the
ulnar, median, and radial nerves are frequently cut across, and in
gun-shot injuries.

_Changes in Structure and Function._--The mere interruption of the
continuity of a nerve results in degeneration of its fibres, the myelin
being broken up into droplets and absorbed, while the axis cylinders
swell up, disintegrate, and finally disappear. Both the conducting and
the insulating elements are thus lost. The degeneration in the central
end of the divided nerve is usually limited to the immediate proximity
of the lesion, and does not even involve all the nerve fibres. In the
distal end, it extends throughout the entire peripheral distribution of
the nerve, and appears to be due to the cutting off of the fibres from
their trophic nerve cells in the spinal medulla. Immediate suturing of
the ends does not affect the degeneration of the distal segment. The
peripheral end undergoes complete degeneration in from six weeks to two
months.

The physiological effects of complete division are that the muscles
supplied by the nerve are immediately paralysed, the area to which it
furnishes the sole cutaneous supply becomes insensitive, and the other
structures, including tendons, bones, and joints, lose sensation, and
begin to atrophy from loss of the trophic influence.

#Nerves divided in Amputation.#--In the case of nerves divided in an
amputation, there is an active, although necessarily abortive, attempt
at regeneration, which results in the formation of bulbous swellings at
the cut ends of