The Open Elbow

A cluttered engineering laboratory in Cambridge in Massachusetts late on a March night, flat light from fluorescent tubes, on a workbench an opened forearm shell of finely ribbed flesh-coloured plastic with a metal ring at its end, beside it an open frame of brushed aluminium with two parallel rails, cross bolts and two small electric motors, a black chassis crowded with green circuit boards, small gears and capacitors, every component plain and unmarked, an amber translucent battery pack, loose wires in red, yellow and blue, a white cable with a red plug, two hands holding a small screwdriver at one motor, an oscilloscope with a green line soft behind.