[Illustration: Fig. 3—Sting of bee. A, One of the needles separated; _a_, the barbed point; _b_, piston; _c_, arm. B, Transverse section of the sting: _dd_, the two needles; _e_, bead for guiding the needles; _f_, director; _g_, channel of poison. (After Carlet.)] The Sting of the bee has been described in detail by Kraepelin, Sollmann, Carlet[3] and others. It is an extremely perfect mechanical arrangement. The sting itself—independent of the sheaths and adjuncts—consists of three elongate pieces, one of them a gouge-like director, the other two pointed and barbed needles; the director is provided with a bead for each of the needles to run on, these latter having a corresponding groove; the entrance to the groove is narrower than its subsequent diameter, so that the needles play up and down on the director with facility, but cannot be dragged away from it; each needle is provided with an arm at the base to which are attached the muscles for its movement. This simple manner of describing the mechanical arrangement is, however, incomplete, inasmuch as it includes no account of the means by which the poison is conveyed. This is done by a very complex set of modifications of all the parts; firstly, the director is enlarged at the anterior part to form a chamber, through which the needles play; the needles are each provided with a projecting piece, which, as the needle moves, plays in the chamber of the director, and forces downwards any liquid that may be therein; the poison-glands open into the chamber, and the projections on the needles, acting after the manner of a piston, carry the poison before them. The needles are so arranged on {7}the director that they enclose between themselves and it a space that forms the channel along which the poison flows, as it is carried forwards by the movement of the pistons attached to the needles. If the needles be thrust into an object quite as far as, or beyond, the point of the director much poison may be introduced into a wound, as the barbs are provided with small orifices placed one above the other, while if this be not the case much of the liquid will flow on the outside of the object.