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

78 INJURIES OF NERVES.
currents of central origin; but this would only hold good
of the motor filaments, and as regards the outer end would
scarcely apply even to the sensitive libres, which would
continue to be excited from without, yet the whole of the
external end changes, and none of the central extremity.
Waller's theory, which attributes the preservation of
the central end to the conservative power of the ganglion
for the sensory root, and of the spinal centres for the
motor root, still remains the most prominent explanation ;
but whether we are to hold, as he held, that these are, as
regards the nerve, direct trophic centres or not, is still a
matter of doubt.
A few observers have been inclined to refer the changes
which follow section to paralysis of the vaso-motors of the
nerve concerned, but such an agency seems hardly competent,
nor could we, admitting it, explain the automatic
regeneration of isolated nerve ends. Whatever be the
character of the neural impression which, setting out from
spine or ganglion, preserves the nutritive integrity of the
nerve to the remotest filaments, it must, in the case of the
sensory branches, be propagated in a direction opposed to
that in which they are traversed by impressions from without.
It would follow from this, either that the preservative
influence exerted by the centres passes along sjiecial
nerve fibres,
— nervi nervorum,
— or that the sensory fibres
are capable of transmitting impressions both centrally and
peripherally.
The difficulty of explanation is increased, however, by
the autogenetic restoration of nerves separated from the
centres, and which I shall presently have to describe, and
of motor nerve ends when united to
also by the repair
sensory nerves which still remain connected with the
centres.
As regards these points, M. Laverran states with
Schift" that there are numerous trophic centres, and that
very certainly the nutritive centre of one nerve may serve