willing to do this for the greater good. reporter: the greater good. you see, john has volunteered to be one of the first people in the united states to participate in an operation to inject stem cells directly into the spine. it s called a phase one clinical trial. this is the first step. no one knows what will happen. here s how john got to this place. a few years ago i was running, playing golf. reporter: and then gradually, literally, he began to lose it. started tripping, foot drop and started catching my foot on bricks and curbs and started losing my balance initially and then developed a limp in my right leg. i ve lost the dexterity, where you can t button buttons and tie shows. i can kick a little bit but can t really pick my legs up. reporter: john has als,