Dr Martin Fairbanks (Beau Bridges) informs his brother (also a doctor), that he "can now quantitively show . . ." that his wacky theories are correct. He no doubt meant to say, "quantitatively". Later, as he's about to remove his brother's brain, he picks up what he calls an "epidural saw". Epidural is a type of anaesthesia, not surgery. At the end of the episode, other doctors refer to the same instrument as an "epidermal saw" - still not the name of a real medical instrument, but at least closer, as "epidermal" refers to the skin.
Carl "says" near the end that Martin had been wrong, touch is the last sense to fail not the first, however Martin said that as part of the ruse. He may not have known that at all, or he may have known the exact opposite. But he had to tell Carl that touch failed first, to cover up the fact that Carl would not feel things that were not actually happening. Such as, the harness rather than an actual hook. And the saw.