Seven
Good News for
Mammals
Stephen D. Smith was the first to induce artificial regrowth with elec-
tricity applied to the limb of a nonregenerating animal. In 1967 Smith,
setting forth on his own at the University of Kentucky after his appren-
ticeship to Meryl Rose at Tulane, implanted tiny batteries in adult frogs'
leg stumps. I followed his work eagerly and was elated to hear that he'd
gotten the same amount of partial regrowth that had resulted from
Rose's salt, Polezhaev's needles, and Singer's rerouted nerves. Of all the
experiments that have influenced me, this was probably the one that
encouraged me the most.
For a battery that was small and weak enough, Smith had returned to
the simple technology of Galvani and Volta. He soldered a short piece of
silver wire to an equal length of platinum wire, and put some silicone
insulation around the solder joint. He chose these two metals as being
the least likely to release ions and produce spurious effects by reacting
with the surrounding tissue. When immersed in a frog's slightly saline
body fluids, this bimetallic device produced a tiny current whose voltage
was positive at the silver end and negative at the platinum end.
Since our work on frog erythrocytes hadn't yet been published, it was
sheer luck that the current from these batteries fell close to the "window
of effectiveness" for blastema formation. As Smith later wrote: "It would
he
nice to be able to say
that
I
had
worked out
all
the
parameters
in
advance, and knew exactly what I was doing, but such was not the case.
As so often has happened in the history of science, I stumbled onto the
right procedure."