Abstract: An indwelling needle assembly comprises an inner needle secured to an inner needle hub, a hollow outer needle in which the inner needle is positioned, an outer needle hub secured to the outer needle and having a projection at the proximal end, and an elastic protector which has a connection member with a projecting part engageable with the projection and which is detachably connected to the outer needle hub by the engagement of the projecting part with the projection. The projection of the outer needle hub comprises a tilted sliding surface on which the projecting part slidingly moves. The connection member can take a first state in which the projecting part engages the projection and a second state in which the projecting part is disengaged from the projection. When changing from the first state to the second state, the projecting part slidingly moves along the sliding surface of the projection.

Abstract: A lancet instrument detachably fitted to a lancing apparatus, comprising a lancet having a lancet body with a sharp lancet tip at its tip, a lancet hub fixed to the lancet body so that the lancet tip is exposed, and an elastic deformation part extended from the lancet hub in the tip direction and elastically deformable so that the distance thereof from the lancet body can be changed, a ring-like member fitted to the outer periphery of the elastic deformation part and releasable in the tip direction by changing the distance between the elastic deformation part and the lancet body, and a casing having a ring-like member contact part storing the lancet so as to be movable in the longitudinal direction and formed in the inner peripheral part thereof so that the ring-like member is brought into contact therewith and stopped to move in the tip direction and a tip opening through which the lancet tip can be projected.