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

NEURO-PHYSIOLOGY. 49
which had their true cause in the upper
nerve.
end of a divided
Neural stimulants.— The various forms of irritation which
may
affect the nerve trunks are capable of classification,
and their character and mode of action are not devoid of
interest to the neuro-pathologist. Laying aside the volitional
stimuli, and those which result from the action of
external agencies on sensory nerves, we shall find in disease
another set, which may
affect like those just mentioned,
not alone the extremities of nerves, whether central or
peripheral, but which may attack the nerves either in these
localities or in their passage to and from the tissues with
which they are functionally related. To this set of irritations
belongs inflammation, with all its consequences of
increased temperature, swelling, and defective
nutrition.
Disturbed mechanical relations of tissues to nerves, tumors,
cicatrices, dislocations, or fractures, may
all come to act as
irritants to neighboring nerve trunks, as well as the near
passage of missiles, the presence of foreign bodies, wounds,
etc. From these varied causes result numerous sensations,
such as numbness, so called, formication, burning, itching,
and, most prominently of all, pain in its endless variations.
The physiologist has studied a class of nerve irritants
which have, for tbe pathologist, only an occasional interest.
These are electricity, heat or cold directly applied
to nerve trunks, desiccation, excess of water and chemical
agents, such as salt, sugar, bile, acid, etc.
The first of these may be set aside for future study.
Our information on these subjects is due chiefly to Eckhardt.
Budge, Kolliker, Klihne, and Bernard.
The first
of these authors pointed out the power possessed by common
salt to excite, without destruction, the nerves of
motion ;
so that Avhen a divided peripheral end is
placed
in a concentrated solution of this agent the muscles are
seen to contract; no such result being attained by weak