Jonathan Metz had been trapped for two days in his Hartford, Conn., basement with his left arm stuck in a broken furnace. Smelling rotting flesh, he decided that amputation was his only hope.So he fashioned a tourniquet near his shoulder and began cutting. He made it almost all the way through, but wasn't able to free himself.He was rescued Wednesday after three days in his West Hartford basement when worried friends called police and firefighters cut the furnace apart.Doctors gave the account of Metz's harrowing experience at a news conference Thursday. They said the attempted self-amputation probably saved his life, preventing the infection in his gangrenous arm from spreading to the rest of his body.