Good News for Mammats 157
This discovery and our own research indicated that the potential for at
least some artificial regeneration was clearly quite good in young mam-
mals. But what about the ones who needed it most—us older folks
whose parts were more likely to be injured or broken down? The answer
came unexpectedly several years later, in a way that showed the futility
of adhering too rigidly to one's original plan. The scientist must be free
to follow unexpected paths as they appear.
I always expected each of my associates, whether student or estab-
lished researcher, to follow some independent project unrelated to our
work together. In 1979, a young assistant named James Cullen (now a
Ph.D. investigator in anatomy at the Syracuse VA hospital) proposed to
study what would happen if nerves were implanted into the bone mar-
row of rats. Jim thought the nerves should induce new bone to form in
the marrow cavity. Since the idea seemed logical and the technique
might supplement the electrical bone-healing devices we'd developed by
then, I encouraged him to go ahead.
Jim ran into technical problems right away. He could easily dissect
the rat's sciatic nerve out of the hind leg, but getting it into the marrow
cavity through a hole drilled in the thighbone was like trying to push a
strand of limp spaghetti through a keyhole. He resorted to drilling two
holes in the femur, passing a wire suture into the outer one, up the
femur, and out the hole nearer the hip. Then he looped the wire around
the nerve and pulled it into the marrow cavity using the suture. How-
ever, after doing a number of these, Jim decided that there had to be a
better way. He decided to amputate the rat's hind leg halfway between
the hip and the knee. He could then drill a hole into the marrow cavity
just below the hip, pass a suture through it, and pull the nerve down
the cavity and out the end of the bone remnant. This was much easier
and made a better connection of nerve to bone, so Jim prepared a
number of animals this way, only to find that the nerve had a disconcert-
ing tendency to pull back, out of the femur. The amputation didn't faze
the rats; they used the stump vigorously, and this caused the nerve to
retract.
In those few animals whose nerve had stayed in place, an interesting
bone formation had appeared in the marrow cavity. To secure the nerve
and look for the same result in other animals, Jim sutured the nerve to
the skin that we closed back over the stump. The stitch held the nerve
in place, all right, but one animal so treated gave us a totally unpre-
dicted and fascinating result: The missing portion of the femur partially
regenerated.
While
this was surprising enough,
the
most
startling
fact
was that Jim had used a group of surplus rats about six month old.
These rats were
well
into adulthood , when
mammals were thought to