the nerves. When there has been suppuration, and
especially if the nerves have been cut so as to be exposed in the wound,
these bulbous swellings may attain an abnormal size, and are then known
as "amputation" or "stump neuromas" (Fig. 84).

When the nerves in a stump have not been cut sufficiently short, they
may become involved in the cicatrix, and it may be necessary, on account
of pain, to free them from their adhesions, and to resect enough of the
terminal portions to prevent them again becoming adherent. When this is
difficult, a portion may be resected from each of the nerve-trunks at a
higher level; and if this fails to give relief, a fresh amputation may
be performed. When there is agonising pain dependent upon an ascending
neuritis, it may be necessary to resect the corresponding posterior
nerve roots within the vertebral canal.

[Illustration: FIG. 84.--Stump Neuromas of Sciatic Nerve, excised forty
years after the original amputation by Mr. A. G. Miller.]

#Other Injuries of Nerves.#--_Contusion_ of a nerve-trunk is attended
with extravasation of blood into the connective-tissue sheaths, and is
followed by degeneration of the contused nerve fibres. Function is
usually restored, the conducting paths being re-established by the
formation of new nerve fibres.

When a nerve is _torn across_ or badly _crushed_--as, for example, by a
fractured bone--the changes are similar to those in a divided nerve, and
the ultimate result depends on the amount of separation between the ends
and the possibility of the young axis cylinders bridging the gap.

_Involvement of Nerves in Scar Tissue._--Pressure or traction may be
exerted upon a nerve by contracting scar tissue, or a process of
neuritis or perineuritis may be induced.

When terminal filaments are involved in a scar, it is best to dissect
out the scar, and along with it the ends of the nerves pressed upon.
When a nerve-trunk, such as the sciatic, is involved in cicatricial
tissue, the nerve must be exposed and freed from its surroundings
(_neurolysis_), and then stretched so as to tear any adhesions that may
be present above or below the part exposed. It may be advisable to
displace the liberated nerve from its original position so as to
minimise the risk of its incorporation in the scar of the original wound
or in that resulting from the operation--for example, the radial nerve
may be buried in the substance of the triceps, or it may be surrounded
by a segment o