Life's Potentials
95
ELECTRICAL MEASUREMENTS ON THE SALAMANDER
wall socket isn't used up when we turn on a light but is merely coursing
through it to the ground, through which it eventually returns to the
power station. Since my measurements were positive over collections of
nerve cell bodies, and increasingly negative out along the nerve fibers, it
seemed a good bet that current was being generated in the cell bodies,
especially since they contained all of the "good stuff"—the nucleus,
organelles, and metabolic components—while the fibers were relatively
uninteresting prolongations of the body. At the time, I supposed the
circuit was completed by current going back toward the spine through
the muscles.
This was a good start, but it wasn't scientifically acceptable proof. For
one thing, my guess about the return part of the circuit was soon dis-
proved when I measured the limb muscles and found them polarized in
the same direction as the surface potentials. For another thing, it had
recently been discovered that amphibian skin itself was polarized, inside
versus outside, by ion differences much like the nerve membrane's rest-
ing potential, so it was just barely possible that my readings had been