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

NEURO-PHYSIOLOGY. 51
patliologist.
As concerns the individual nerve, the facts
are as follows:
"When a nerve is placed in a dense solution of certain
salines it is at first excited, and then finally loses its functional
powers, which may again be restored by placing it
in water.
If a nerve be slowly and carefully desiccated to a certain
it is ex-
degree by warmth, or mere exposure to the air,
cited for a time so as to convulse its connected muscles,
and at last ceases to be irritable until moistened anew.
On the other hand, when we place nerves in distilled
water, they lose their capacity to be excited, but regain
it again when the balance is restored, by soaking them in
weak solutions of phosphate of soda. Indeed, so delicate
is the status of the nerve, so easily is it disturbed, that
mere separation from the centres, or exposure short of
perceptible desiccation, modifies the excitability of the
fibres.
We have thus learned that every modification in the
amount of water, either towards desiccation or towards
excess, tends to alter, and finally to abolish, the neurility
of a nerve, while a restoration of the aqueous suppl}^ or
a loss of fluid by the water-soaked nerve, will, in either
case, suffice to restore its function.
As I have previously said, these are purely physiological
experiments, and nothing akin to them is seen in man, except
by rare opportunity in wounds exposed to improper
dressings, or on the surface of ulcers. At first thought
it
might seem as if conditions of anoemia or hydrsemia
oflfered some analogy to that one of the conditions just
now described as an oversupply of fluid to the nerve ;
but in hydrsBmia, the pathological approach to this state,
there are probably more complex changes in the nutritive
supplies besides those arising from a too fluid blood.
The opposite condition is best represented among diseased