Gliding into the operating room for the first time to assist a surgeon, Penelope wasn't nervous.

Unlike other novice medical assistants, "she" felt nothing. That's because Penelope is a robot, a machine that recently made medical history as the first to act as an independent surgical aide during an operation.

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During a procedure in June at New York-Presbyterian Hospital to remove a benign tumor from a patient's forearm, Penelope responded to voice commands from a surgeon, handing over clamps, forceps and other instruments with its magnetized mechanical arm. Watching with digital cameras, the robot retrieved the instruments when the surgeon put them down.

Inside its computer brain, artificial intelligence software kept track of the instruments to ensure none was misplaced and predicted what tool the surgeon would ask for next.

"Penelope is just the first step," said Dr. Michael Treat, a surgeon, physicist and lifelong robotics fan who founded the company that developed Penelope.

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The robot, named for the resourceful wife of Odysseus in Homer's epic poems, weighs 60 pounds and has a lightweight arm of carbon fiber mounted on a stainless steel frame.