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

NEUKO-PHYSIOLOGY. 43
Bej^oncl a doubt, certain electrical phenomena
exist in
connection with all nerves and in the presence of all
nerve action ;
but so far from these facts showing that
nerve force is electricity, their whole bearing is to prove
quite the contrary.
There seems, indeed, to be every likelihood that the
electric states which arise during nerve disturbance are
merely manifestations related to the states of nervous
activity, and passively dependent, directly or indirectly, on
nutritive changes or upon molecular alterations, themselves
connected with the altered polarity of the nerve during
its conditions of rest or excitation.* More probably nerve
force depends, like magnetism, upon peculiar conditions
of certain matter for its manifestations, so that only where
these exist can it be studied, while, as regards its kinship
to electricity,
we can only surmise that they are correlated,
and that the one may give rise, under certain conditions,
to the production
arguments against their identity,
of the other. Besides the common
such as the fact that
crushing the nerve destroys its power to convey impressions,
while it may still conduct electricity, there are certain
other objections to the conception of their oneness
which appear to me to present insurmountable obstacles
to any such belief. The most formidable of these is the
difference in the speed with which the galvanic and the
nerve currents are propagated. Thus, in the frog's nerves,
at a temperature of 52° F. up to 70° F., nerve force moves at
second. In man it is esti-
a rate of from 81 to 126 feet per
mated to travel on motor nerves at a speed of 200 feet a
second. In sensory nerves the rate at which impressions
move is about 110 feet per second, with some variation for
the different nerves.
It has also been shown by Munk that
the speed
is not uniform for all parts of a given nerve.
If
* Vulpian, p. 104.