The Ticklish Gene
141
was any way he could make sense of the contradictory observations. He
replied in the negative but sent our inquiry to Dr. Bowden, who had
done the actual work on frogs as his doctoral thesis. Bowden had a
possible explanation. He'd done the experimental work under a time
limit, and to finish before the deadline he'd kept his frogs at high tem-
peratures—only a few degrees short of killing them, in fact—in order to
speed up their metabolism.
Bowden also mentioned that two researchers cited in his bibliography
had seen fracture healing in frogs much the same way we had. In the
1920s, a German named H. Wurmbach, also working on his doctorate,
noted some strange cellular transformations in the blood clot and wor-
ried over his inability to explain them. However, Wurmbach also found
mitoses in the periosteum and ascribed healing to the latter process,
since it didn't involve dedifferentiation. A decade later, another German
scientist, A. Ide-Rozas, saw the same changes in the blood cells, but he
was more daring. He proposed that this transformation was the major
force behind fracture healing in frogs and further suggested that re-
generating salamanders formed their limb blastemas from nucleated red
blood cells. Other experiments seemed to contradict Ide-Rozas' idea
about limb blastemas, so his work was discredited and ignored, but
Bowden wished us better luck.
Bowden's letter gave us a framework for understanding our results.
We already knew that mammals did not heal bones by dedifferentiation
of their red corpuscles, because their red cells had no nuclei and thus no
mechanism for change. Mammals also had a thicker periosteum than
other vertebrates, so we reasoned that periosteal cell division played a
larger healing role in mammals. Frogs, it seemed, had both methods
available but activated the periosteal cells only at high temperatures.
Do-lt-Yourself Dedifferentiation
Now we were sure that our results were real. We repeated the same
fracture studies, but this time we also observed the cells while they were
alive. We took tissue samples from the fractures and made time-lapse
film sequences using techniques like those in the movie that had im-
pressed me so much at the NAS workshop. We confirmed that the
changes began in the first lew hours, just after the electrical forces
reached their peak.
Now we decided to try a crucial test. If the electricity really triggered
healing, we should be able to reproduce the same field artificially and start