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

24 INJURIES OF NERVES.
highest level and attached to a string, which passed over
a little roller and carried a pan on which weights were
placed. The nerve was then tested by mechanical and
electrical irritation, and having been found to respond,
weights were placed on the scale-pan, and these, with the
amount of stretching of the nerve, were noted. In this,
and in other experiments on frogs, it seemed to me that
the nerve bore best a slow addition of a weight, which,
suddenly added, caused abrupt loss of physiological properties.
As the extension was increased, the muscles were
thrown into a state of irregular convulsive activity,
which
did not cease altogether when the nerve was for a time
allowed to relax. Slight mechanical injuries ceased to
cause reaction when the nerve had elongated to the extent
of one-fifth, but electricity still
produced muscular contraction
until the lengthening was equal to | of an inch in
three inches. It is very probable that much less stretching
will be found competent to destroy the perfect control
of the will over the muscles, or to interfere with the conveyance
of delicate sensory impressions to the centres.
I have seen a curious illustration of the degree to which
a nerve may be meddled with before losing its power to
carry impressions. In a case of hospital gangrene of
the thigh, resulting in an enormous cavity, the sciatic
nerve was left intact.
During one of the dressings, this
large trunk was at iirst quite roughly drawn out of the
wound, and afterwards pushed down to the bottom or
side of the cavity by the dressing employed. Some pain
resulted, as may be supposed, but the sense of touch
was scarcely disturbed. I witnessed the removal of
the dressings. The nerve must have been pushed fully
four or five inches out of its patli, and very much
elongated.
The fibrous nature of the coarser nerve sheaths serves to
protect the fibres from the ravages of disease, of which fact