Injuries of nerves and their consequences - Reflex Sympathetic ...

PATHOLOGY OF NERVE LESIONS. 79
a like end for another, and that perhaps by means of anastomoses,
and after a certain lapse of time, the trophic centre
of neighboring nerves may come to answer a similar purpose
for the peripheral extremity of the divided nerve.
Of this, however, we have no proof. We only know that
completely isolated nerve ends may undergo repair without
having, so far as we are aware, any connection with
the centres. When, therefore, nerves are cut, the perineural
covering, the sheath of Schwann, and probably
the axis cylinder, rest unaltered, while the myoline or
white substance
of Schwann breaks up, becomes granular,
and disappears completely.
Regeneration of nerves. — When the nerve has reached its
final term of change, a new process begins, which may or
may not result in its functional restoration. After a nerve
has been divided, and a portion exsected, it either remains
separated, or the two portions reunite with more or less
completeness. In both cases the nerve fibrils of the
peripheral extremity undergo a reparative change, so that
we have two sets of conditions under which to stud}- the
progress of restoration.
Within two months after section, the upper end of
the nerve is seen to exhibit a slio^ht enlargement, from
which projects a grayish, conical bundle of delicate fibres.
Many
of these are
normal in appearance, others want, at
first, the medullary matter. As this stem extends towards,
and finally reaches, the peripheral nerve end with
which it unites, the fibres increase in number and in bulk,
the complete fibres becoming more numerous as the tint
of the new formation changes to the healthy white color
of normal nerve tissue. After some months, it may acquire,
what at least in my experience has been rare, the
full size of the nerve ends which it joins together.* In
* Yulpian, p. 256, op. cit.