Sounds like you have the original wiring added sometime after 1885. You have three choices, use a remote system like an X10, add electrical boxes to the walls and pull wires from the box up to the ceiling fixture. Power will run to the ceiling fixture exactly as it does now, then via the new romex down to the wall switch and then back up the same romex. A floor beneath and attic will be the easiest and least destructive to do. Or third use an exposed raceway system.