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medieval prosthetics were designed for specialized knightly needs,such as an artificial knee built in a semiflexed position that allowed a knight to ride his steed, although it did not support sitting or standing.

Sixteenth-century warfare also motivated the French physician Ambroise Paré to develop innovative procedures that made him a founding figure for modern surgical practice and amputation medi- cine. His wide experience as an army surgeon gave him ample ac- quaintance with severe injuries,and he introduced artificial eyes (made of gold and silver) and teeth, and a prosthetic leg. One invention,Le Petit Lorrain,was a hand operated by springs that an officer in the French army used in battle.

As in the history of automata, this phase of the development of prosthetics relied on the work of mechanical experts such as armorers and watchmakers, and on the growing knowledge of anatomy. But still the technology was not sufficiently advanced to make devices that were both functional and natural looking, or to make limbs that were easy to use. Iron prosthetics were heavy, and their only source of power was either a natural hand that set and adjusted the artificial unit, or other muscles in the body. Beginning in 1818 and continuing to modern times, inventors have developed harnesses and levers that carry power from other parts of the body, such as the shoulder, to make an artificial hand, say, open and close its grasp.

Natural appearance often had to be sacrificed to functionality, and power to operate a limb was hard to come by. Nevertheless, early inventors improved prosthetic devices through the ingenious use of materials.In 1800, for instance,James Potts of London designed a false limb that came to be known as the Anglesey Leg,because it re- placed a leg lost by the Marquis of Anglesey at the Battle of Waterloo. Among its advanced features was an articulated foot that could be controlled by catgut strings, extending from knee to ankle, which determined the position of the foot by transmitting motion from the knee.These cablelike control elements have natural parallels; for ex- ample, tendons that stretch back to muscles in the arm control the fingers of our hands.Along similar lines, one modern breakthrough is the development of artificial muscles that work like real ones.

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