to driven capstans 18 a and 18 b by a screw clip or other suitable fastener however the work members may also be permanently affixed to the driven capstans by soldering or welding or the like or may be formed in one piece with the driven capstans work members 20 a and 20 b together comprise one form of surgical end effector other surgical end effectors may be used in the surgical instrument of the present invention end effectors simply may comprise standard surgical or endoscopic instruments with their handles removed including for example retractors electrocautery instruments microforceps microneedle holders dissecting scissors blades irrigators and sutures the end effectors will typically comprise one or two work members proximal portion 28 a of instrument 12 includes support brackets 98 and 102 which are connected together by a support rod 100 as well as two guide rails 104 and 106 a rotary bearing 91 forming rotary joint 26 is housed within support bracket 98 for supporting tubular support member 24 sliding bracket 96 is slidably mounted to guide rails 104 and 106 along linear bearings as shown in fig1 sliding bracket 96 is connected by bracket 36 to positioning mechanism 14 sliding bracket 96 preferably has about 8 inches of travel for surgical applications drive motors m 1 m 2 m 3 m 4 and m 5 are mounted to sliding bracket 96 and drive respective cables c 1 c 2 c 3 and c 4 and c 5 sliding bracket 96 supports each of the drive motors during operation sliding bracket 96 is connected to positioning mechanism 14 by mounting bracket 36.