Electrography of the striatum and pallidum was guided by the consideration that it may provide an answer as to the participation of these structures in the mechanism of extrapyramidal and convulsive disorders. In an individual case such recordings may help to decide whether elimination or reduction of the activity, particularly of parts of the pallidum, may serve a useful purpose: postoperatively, such recordings may give an indication as to whether the procedure employed was able to change the functional state of the pallidum. MATERIAL AND METHODS Since the recordings and operative procedures had to be performed in several stages, a new type of stereoencephalotome (Model V) was constructed. It permits one to apply the apparatus repeatedly in exactly the same position. The apparatus is fixed to the skull by means of four screws that carry small steel balls, to which the feet of the stereoencephalotome may be attached in any