(1687) if possible , what was the cause of the great pain , and the swelling of the skin , which we experience through the sting of the Gnat .Well , I could not discover that the Gnat , when it is about to prick , pushes its Sting out of the upper end of the sheath , although I did find ( but very seldom ) that the Gnat pushed a small part of itsThe stinging of the gnat .Sting out of the top of the sheath : But I invariably found that the Gnat fully opens its sheath on one side of the same , just as if we imagine having a sword in its scabbard , and that the leather of the scabbard , at one side , was only lying against the other side ; in such a way that , if one wished to use the sword , one need not draw it out of its scabbard , but that the scabbard , by being touched there , would fully open on one side .