Artificial limbs have come a long way from the wooden legs and
plastic arms of old: Today's prosthetics take messages directly
from the brain. Their performance far exceeds that of the
previous generation of devices, which required concentrated
effort to make ungainly motions. "You think, and then your
muscles move," a woman who has one of the newer artificial arms
tells the New York Times. The new arms are complicated and
expensive, and implementation requires preserving nerves from
the amputated limb. Those nerves are then attached to chest
muscles, where tiny electrodes watch for the body's natural
nerve signals and radio them to the arm. With the new
technology, amputees can manipulate small objects like balls and
shoelaces without having to concentrate more than any other
person.