186
The Body Electric
tude and force (amperage and voltage) of current could serve as a vector
system giving distinct values for every area of the body. The electric
field surrounding continuously charged cells and diminishing with the
distance from the nerve would provide a third coordinate, giving each
cell a slightly different electrical potential. In addition, a magnetic field
must exist around the current flow, possibly adding a fourth dimension
to the system. Together these values might suffice to pinpoint any cell
in the body. The electric and magnetic fields, varying as the current
varies with the animal's state of consciousness and health, could move
charged molecules wherever they were needed for control of growth or
other processes. Since currents and electromagnetic fields affect the cell
membrane's "choice" of what ions to absorb, reject, or expel, this sys-
tem—in concert with the chemical code by which neighboring cells
recognize each other—could precisely regulate the activities of every
cell. It could express the exact point along the limb at which new
growth must start; distinguish between right and left, top and bottom;
even explain how totally missing parts, like extirpated bones or all the
little bones of wrist and hand, can reappear.
Furthermore, the difference between electrical values at the inner and
outer edges of the blastema would lessen as a new limb grew behind it.
(Remember that the electrical potential grows increasingly negative
toward the end of an intact limb.) The gradual convergence of these two
values could constitute a feedback signal perfectly reflecting the number
of dedifferentiated cells still needed. Although the results weren't en-
tirely conclusive, perhaps because measurements had to be made under
anesthesia, several experiments in the 1950s suggested that such a volt-
age differential governed restitution of the proper number of segments in
earthworms. There was even a surge of positive potential that seemed to
indicate when the job was finished.
This is a rich concept, and the details are without doubt more com-
plex than this sketch, but they're all open to experimentation in a way
that Weiss's morphogenetic field and Burr's L-field were not. The best
part of this two-stage analysis is that it gives us a rationale for trying to
foster regeneration after human injuries before we know all the details of
the second phase.
The rat limb experiments strongly suggest that mammals lack two
crucial requirements for the first phase of regeneration: They don't have
the necessary
ratio of
nerve tissue to
total limb tissue,
the amount
needed to make the dedifferentation stimulus srong enough; and they
lack sufficient sensititive cells to respond to the electrical stimulus and
form a big enough blastema. The work on rats pointed the way to defin-