Abstract: Forceps instrument comprising a sheath having a first end and an elongated maneuvering element slidably disposed in the first end of said sheath. The sheath has an axis. The instrument comprises two jaw-pieces, at least one of the jaw-pieces being movable away from and toward the other of the jaw-pieces when the maneuvering element slides axially in the first end of the sheath. The jaw-pieces have, in an extension of a part thereof, an arm extending progressively toward the axis of the sheath so as to form a first, internal, inclined surface extending progressively toward the axis and facing the latter and a second, external, inclined surface extending progressively toward the axis and facing the internal surface of the sheath. The arm has a convex excrescence which is slidable substantially against the internal surface of the sheath, the excrescence having a concave hollow cavity facing the axis.