Your heart beats about 100,000 times every day. It pumps blood to every part of your body. But sometimes a heart becomes too weak to keep working. On December 1, 1982, a surgeon named Dr. William DeVries tried something no one had done before. He implanted a machine called the Jarvik-7 into a patient named Barney Clark. The Jarvik-7 was an artificial heart made of aluminum and plastic. It was connected to a large machine outside the body by two tubes that ran through Clark's chest. The outside machine, called a compressor, pushed air through the tubes to make the heart pump. Clark could not walk far from the machine. He was tethered to it at all times. Clark lived for 112 days with his new heart. He had many health problems during that time, but the heart itself kept beating. His case proved that a machine could replace the human heart, at least for a while. Scientists kept working to make artificial hearts smaller and better. Today, some heart devices are small enough to fit inside the body completely. Clark's pioneering surgery opened the door to saving thousands of lives.