190
The Body Electric
shown that the few live cells remaining in the paste don't survive and
the bone particles themselves soon dissolve. Instead, some substance
from the disintegrated bone stimulates repair. Since its first successful
trial on humans by several Russian surgeons in the mid-1960s, this
method has gradually come into increasing use in the Soviet Union.
Eyes
There is at present no indication whatsoever that humans could ever
regenerate any part of their eyes, but the ability of newts (salamanders of
the genus Triturus) to do so makes this a tantalizing research ideal for the
far future. If the lens in a newt's eye is destroyed, the colored cells of the
top half of the iris extrude their pigment granules, then transform by
direct metaplasia into lens cells. They soon start synthesizing the clear
fibers of which the lens is made, and the whole job is finished in about
forty days. In case the iris is gone, too, a newt can create a new one from
cells of the pigmented retina, and those cells can also transform into the
neural retina layer in front of them. If the optic nerve gets damaged, the
neural retina in turn can regenerate the nerve tract backward and recon-
nect it properly with the brain.
SALAMANDER EYE-LENS REGENERATION