Much beautiful mechanism is observed on a microscopic examination of this weapon and its appendages, so powerful in comparison with their bulk. The sting is composed of three separate portions, _i. e._, two sheaths (as seen in Plate II., fig. 4) and the barb. The sheaths, which are attached to the powerful muscles on either side at _s_, are first protruded in the act of stinging, and, clasping the barb, enables the insect to bury it in the flesh to the depth of one-twelfth of an inch; at the same time, by a muscular contraction, the poison is forced along the groove, and the barb enters the wound, causing the well-known painful effects which arise from the sting of a bee. The darts composing this instrument are furnished with teeth or barbs, set obliquely on their outer side, which give it the appearance of an arrow, and by which it is retained in the wound until the poison has been ejected. If the sufferer could only command himself so as to remain perfectly passive, the bee might be able to draw in these barbs which protrude beyond the sheath, and would then have a chance of withdrawing the sting: the little insect would consequently inflict less pain, and might perhaps escape paying the penalty of her life. It generally happens, however, that the excitement of both parties is so great, that the poor bee leaves behind the whole apparatus, and even part of her intestines, so that her death is the result, and the wound is more severe. The sting is about the sixth part of an inch long, and is largest at the base. Here are situated the glands or ducts (Plate II., fig. 4, _u_). By these the poison is secreted, and passed into the poison-bag (Plate II., fig. 4, _f_), which acts as a reservoir for retaining it till required. On the subject of the sting, Paley remarks:--"The action of the sting affords a beautiful example of the union of chemistry and mechanism: of chemistry, in respect to the venom, which in so small a quantity can produce such powerful effects; of mechanism, as the sting is not a simple, but a compound instrument. The machinery would have been comparatively useless had it not been for the chemical process, by which, in the insect's body, honey is converted into poison; and, on the other hand, the poison would have been ineffectual without an instrument to wound, and a syringe to inject the fluid."