The Self-Mending Net
211
As far as I know, the only electrical measurements of spinal shock in
mammals were preliminary ones done at our laboratory in conjunction
with Carl Kao of the VA hospital in Washington, D.C. We tested the
severed cord ends in cats for twenty-four hours and found only an in-
creasing positive potential. The situation seemed quite similar to the
electrical difference between salamander and frog limbs. As in most in-
stances, positive potentials appeared to inhibit constructive cellular ac-
tivity while negative ones fostered it.
An experiment Kao did several years ago provided some supporting
evidence. Kao made two cuts through the spinal cord in each of several
cats, producing a central fragment about 5 millimeters long, separated
from each end. He then grafted pieces of sciatic nerve as spacers in the
two cuts. Typical degeneration with cysts occurred in each end of the
cord but not in the isolated piece. In fact, this part showed some growth
of its ependyma and nerve fibers. The small piece was probably isolated
from the positive potentials produced in the rest of the cord. Hence it
escaped inhibition and grew. It seems the prolonged electrical positivity
of spinal shock is the main roadblock in the way of human cord repair.
KAO'S EXPERIMENT
It should
be possible to cancel that polarity and replace
it with a
growth-stimulating negative one, using
a
properly shaped electrode.
Older injuries in which spinal shock
has subsided might require a dif-