Abstract: Activity in different fibers of a nerve in an animal can be selectively blocked by applying direct electric current between an anode and a cathode attached to the nerve. The anode has base of silver foil with a tough shaped portion which has a first curved region coated with silver/silver chloride for contacting the nerve. The cathode includes a silver foil base which also has a tough shaped portion with a second curved region coated with silver/silver chloride for contacting the nerve. The second region is at least six times greater in area than the first region, so that the density of current conducted between the cathode and the nerve is significantly less than the current density at the anode. A signal generator produces a direct current stimulation signal between positive and negative output terminals that are connected respectively to the anode and cathode.