160
The Body Electric
Another experiment showed us a formidable obstacle, however. In an
additional series of rats we made a neuroepidermal junction, not at the
end of the amputation stump, but on the side of the leg. There we
measured the same "regenerative" electrical changes, but nothing hap-
pened. There was no growth. This meant that there were no sensitive
cells at this site—no cells able to dedifferentiate in response to the cur-
rent. In mammals, it seemed, such cells were found only in the bone
marrow, a sparse cell population to serve as a source of raw material,
especially in adult animals.
AN
ARTIFICIAL
NEUROEPIDERMAL
JUNCTION
STARTS
REGROWTH IN RATS
This explained why we never got complete regrowth in any of our
rats. The results were typical of an inadequate blastema. There weren't
enough sensitive cells in the bone marrow to make a blastema big
enough to produce a whole leg. The prospects for full limb regeneration
in humans, then, looked very dim—unless we could come up with a
way of making other cells electrically sensitive so as to transform them
into despecialized blastemal cells. Luckily, while working on a com-
pletely different problem described in the following chapter, we stum-
bled upon a way to do just that.