1. In an orthodontic appliance having a harness for mounting on the head of a patient and a corrective tractive apparatus applied to a selected portion of the dental-facial frame of the patient, the improvement comprising a constant-force negator extension member located on each side of the patient''s head, each of said members including a coil having an outer end, said coil having properties which permit it to exert a constant force when in use, means for supporting said coil, means connecting said outer end to one of said harness and apparatus, and means connecting said coil supporting means to the other of said harness and apparatus.

6. An orthodontic appliance for applying a predetermined constant tension to a selected portion of a dental-facial frame of a patient comprising a harness for mounting on the upper portion of the patient, a corrective tractive apparatus selectively applied to the dental-facial frame of the patient, constant-force means connected to said harness at each side of the patient''s head, said constant-force means including a housing, a negator extension member mounted within said housing, said negator extension member including a coil formed to a predetermined radius of curvature and having properties which permit it to exert a constant force at all times, operating rod means connected to said corrective tractive apparatus and extending into said housing, and means connecting one end of said operating rod means to said negator extension member for extending and retracting said coil in response to relative movement between said harness and said apparatus.