I'm watching the classic Trek episode, Dagger of the Mind, on Space. It's the first episode where Spock gets his Mind Meld on. Anywho, he explains that it's very dangerous, because he needs to physically alter blood flow, pressure, nerve connections, and the like. He takes care to caution McCoy that because he's not touching him, McCoy can't be affected. This impiles that it can only be done on beings close to Vulcans, physically, or beings where they've figured out the appropriate changes to make. Later in the same series, of course, Spock does it through walls, on beasties that are based on silicon instead of carbon, and so on. And I realized that, although Enterprise is taking this whole creative license thing a bit too far, Star Trek: TOS never really bothered being consistant from episode to episode, let alone season to season, let alone (really!) series to series.