The Ticklish Gene
137
it so as to offend no one. He stressed that fracture healing should be
considered a vestige of regeneration. Most past work on fractures had
described what happened when a bone knit, as opposed to the how and
why. As Pritchard pointed out, "Not a great deal of thought has been
given to the factors that initiate, guide, and control the various processes
of bone repair." Just as in regeneration research, this was the most im-
portant problem about fractures, he concluded.
Dave and I had to wait several hours before our flight back to Syr-
acuse. We sat in the airport lounge and talked excitedly about broken
bones. Dave agreed that, since I'd found electrical currents in sala-
mander limb regeneration, it was at least plausible that similar factors
controlled the mending of fractures. Having just deciphered the control
system for stress adaptation (Wolffs-law growth) in bone, I felt pre-
pared to get back to the more complex problems of regeneration via its
remnant in bone healing. Dave and I decided to collaborate, and we
planned our experiment on the plane. We would break the same bone in
a standardized way in each of a series of experimental animals. I would
study the electrical forces in and around the fractures as they healed. We
would kill a few of the animals at each stage of healing, and Dave, an
expert histologist (cell specialist), would make microscope slides of the
healing tissues and study the cellular changes. Along the way we would
fit our findings together to see whether electricity was guiding the cells.
Our first task was to choose the experimental animals. We wanted to
use dogs or rabbits, since ultimately we were trying to understand hu-
man bones and wanted to work with animals as closely related to us as
possible. But we would need scores of them to study each phase of heal-
ing adequately, and we had neither the funds nor the facilities to house
so many large mammals. We thought of rats, but their longest bones
were too short to study clearly and were curved as well. We were look-
ing for nice, long, straight bones, in which we could produce uniform
breaks.
We settled on bullfrogs. They were cheap to buy and care for; we
could even collect some ourselves from nearby ponds. I already had a lot
of experience in working with them. Best of all, the adult frog's lower
leg had one long boneāthe tibia and fibula found in most vertebrates
had merged into a tibiofibularis. It was about two inches long with a
fine, straight shaft.
Our misgivings about the evolutionary distance between frogs and
humans were allayed when we went to the library to read up on what
was then known about fracture
healing in
frogs. Dr. Pritchard himself,
along with
two of his students, J. Bowden and
A.
J.
Ruzicka, had