The word for today is "vestigial", meaning "an organ or part of the body degenerate, rudimentary, or atrophied, having become functionless in the course of evolution". In Tom's poor case, he is tormented by a twisted version of this, courtesy of his twin brother. "Hand", drawn by Ross Andru and Mike Esposito appeared in MISTER MYSTERY #1 (Stanley Morse, September 1951).
There's also a scene in this story that you won't see these days: Tom and his doctor light up and have a smoke while the doc discusses his case!
