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commands from a brain that brings in other sensory information such as visual data to forecast changing circumstances. An artificial hand has no sensory feedback that allows the brain to adjust the hand so that it can delicately grasp a teacup without breaking it, or apply full power to twist the cap off a jar. A truly bionic limb needs sensory capability and processing power (in the limb itself, or through con- nections to the brain) as well as appropriate movement, flexibility, and appearance. In fact, what is needed to make a functional bionic limb for a person is nearly identical to what is needed to make a robotic limb.

This is where digital electronics connects with prosthetic science. Some prosthetic limbs now incorporate electronic sensors and com- puter chips to make a smart leg.A direct neural connection be- tween artificial limb and brain is further off,but here, too, initial results have been obtained, using connected or implanted digital electronics. In a way, the eighteenth-century belief that electricity could invigo- rate the body and even animate a dead one is becoming realizable in the twenty-first century, through artificial devices that operate elec- tronicallya trend that began when electricity was first introduced into the body.


In the eighteenth century, although electricity was known to stimu- late the body, its physiological effects were not studied in detail.Nine- teenth-century physicians began experimenting with the influence of electricity on the heart. In 1888, it was found that fibrillation of the heartthat is, the sudden change of a regular beating pattern into an irregular rapid onecould cause sudden death, and in 1899 research- ers found that a strong electrical shock could defibrillate an animals chaotically beating heart.The first human heart was successfully defib- rillated in 1947, and both external and implanted defibrillators were developed in the 1950s and 1960s.

The heart pacemaker is a related and even more helpful bioelectronic device. It sends timed electrical impulses to the heart

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