in dystonia musculorum deformans, if an attempt is made at plantar flexion of the foot when the foot is in dorsal spasm the only response is an increase of the extensor, or dorsal, spasm; if, however, the patient is told to extend the foot that is already in a state of strong dorsal flexion, there will be a sudden movement of plantar flexion; the same phenomenon, mutatis mutandis, is observed when there is a condition of strong plantar flexion.
