Abstract: A method of packing elongated porous bodies moved between zones of different pressure, wherein the porous body (T) reciprocates through a pressurized packing agent (M). The packing agent is thixotropic and is supplied continuously to the porous cable (T) under a pressure exceeding the pressure in a higher pressure zone (P.sub.1) while the porous body (T) is impregnated with a thixotropic packing agent (M) such that the cross-section of the cable, throughout its entire length, is filled with packing agent (M). A hydraulic cylinder-type actuator utilizes a porous cable power transmission element packed in a chamber (7) filled with viscoelastoplastic material and communicated with means designed to develop in said chamber a pressure exceeding the pressure of the actuator working fluid.