Abstract: A medical instrument for use in combination with an endoscope having an operating shaft and a pair of tongs. The instrument has a drive mechanism provided between the operating shaft and the tongs, for opening and closing the tongs. The drive mechanism can apply an additional force to the tongs even after the tongs have closed completely.

Abstract: An endoscopic sheath of the present invention comprising a tubular sheath section having a distal end portion and a hole which extends throughout the length of the sheath section and through which an insert section of an endoscope having observation device can be passed, at least the distal end of the distal end portion opening, and at least the distal end portion being formed of a transparent material, and positioning device for positioning the insert section of the endoscope in the sheath section so that at least part of the distal end portion of the sheath section can be within the view range of the endoscope.

Abstract: A surgical instrument for treatment in the body cavity, in which an open-close member for treatment is rockably mounted by of a pivot pin on the distal end portion of a sheath to be inserted into the body cavity, and is connected to the distal end of a rod passed through the sheath, by a cam mechanism including a cam groove and a cam pin in engagement therewith. As the rod is moved by an operating handle, the cam mechanism is activated to open and close the open-close member for treatment. The component members of the cam mechanism have external shapes such that those portions on the proximal end side of the position near the pivot pin do not project from the sheath in every operating state.