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

REMOTE SYMPTOMS. 177
have been made at more or less remote periods, so that
it is quite probable that were a case of divided nerve examined
at all its stages, we should find at first a rise, and,
after a time, a fall of temperature. Augustus ^Yaller
has left on record a valuable set of experiments which,
to some extent, cast light on this subject. lie submitted
the ulnar nerve at the elbow to the influence of a freezino;
mixture of ice and salt, or to that of ice alone. At
first the mercury fell slightly, but so soon as the nerve
became more completely chilled, and before all sensation
was absent, the temperature between the third and fourth
fingers rose several degrees above that of the interspace
between the first and second digits.
When the cold was
removed and the nerve thawed, the temperature fell, until,
in the two parts mentioned,
it became equal. The physiological
interpretation of these phenomena is a simple
one. The first influence of cold is to irritate the vasomotor
nerve fibres, and thus to occasion a contraction
of the related blood-vessels and a fall of temperature.
Whether this be due to a direct influence on these nerves
or to a centrally reflected impression, is not decided by
Waller's observations. As the main nerve becomes frozen
and ceases to convey messages, the vaso-motors being
paralyzed, their connected vessels undergo dilatation,
the temperature rises, and the part flushes, pulsates, and
feels full. When, in one instance, the ulnar nerve was
more severely frozen by the use of ice and salt, the temperature
rose as described in the last experiment; but the
application of the freezing mixture having been too prolonged,
there was total loss of motion and sensation,
which only very slowly grew better, and for some days the
temperature remained below that of the portions of the
hand to which are distributed the median and radial
nerves.
In this observation, the physiological conclusions
as to the later stages of the paralysis were the same as