13Ô
EXPERIMENTS ON THE
nerve retained its irritability for a certain period, still, if the union of
the two portions were prevented, the irritability was afterwards lost;
so that when at the end of two months the galvanic stimulus of a sin¬
gle pair of plates was applied to the lower portion of the nerve, it
produced no contractions in the muscles to which the nerve was dis¬
tributed. Even when applied to the muscles themselves, the galvanic
stimulus in several cases did not excite contracfion. The experiments
on rabbits made by me, are, therefore, more in favour of the supposi¬
tion of reproduction of the nerve than opposed to it. In the third ex¬
periment only the irritability in the lower part of the nerve was
almost completely lost, (although the nerve was allowed to unite,)
and in this case, therefore, it seems that the nerve had cicatrised, but
that the nervous communication was not restored. Since it appears
from Sticker’s experiments that, unless their communication with
the brain and spinal cord is maintained, nerves cannot preserve their
irritability for any length of time, the mere fact that the lower por¬
tion of a divided and reunited nerve is irritable after the lapse of
several months, proves that the union of the nerve restores in some
degree the nervous communication.
Schwann has recently performed an experiment, which clearly
proves the fact of the reproduction of nerves in the frog:—He divided
the ischiadic nerve in the middle of both thighs; after the operation,
the frog at first leaped but rarely, generally moving only by crawl¬
ing; after a month it leaped more frequently, and at the end of
three months this movement was performed almost as well as by
any other frog. By the aid of the microscope, however, the now
united nerve, at the place of division, was seen to contain nervous
fibrils, lying close together and running its whole length, and the
transparent aspect seemed to result only from the neurilema being
less perfectly reproduced. The fibrils were continuous with those
of the two ends of the nerve, and the stretching that was necessary
for the microscopic examination fully accounted for the nervous
cylinders being, at some points, connected only by very delicate
threads. The upper end of the nerve was enlarged, as is the case
with the ends of nerves in the stump of an amputated limb; the
lower portion did not present the same appearance. The nerve of
the other side could not be examined. The fact of the reproduction
of the nervous fibres after the removal of a portion of a nerve has
been confirmed by Steinrück. (Froriep’s Notiz. Dec. 1838.)
Without the reproduction of the nervous substance which has been
thus demonstrated by Schwann, the experiments of Haighton, Pré¬
vost, and Tiedemann are inexplicable. Tiedemann divided in a dog,
the nerves of the fore-foot and leg, namely, the ulnar, radial, median,
and external cutaneous nerves, in the axilla, and at the expiration
of eight months observed a return of sensation and motion, which
was still greater after twenty-one months; and at last the dog re¬
gained the complete use of the foot. This experiment is most con¬
vincing with reference to regeneration of nerve. The return of
some degree of sensation in transplanted flaps of skin, even after the
division of the portion by which it was connected to its original