To enter with any fulness into the history, literature, and varieties of this operation, and the instruments required, would in itself require a large volume. Suffice it here to describe the case suitable for the operation, the essentials required in the instrument, and the method of performance. 1. _For a case to be suitable_ the _stone_ should not be too large, and especially not too hard, also there should not be too many of them. The _urethra_ should be capacious enough to let the instrument pass easily and painlessly. The _bladder_ should be large enough to contain four ounces of water at least, should not be much inflamed, and, on the other hand, should not be paralysed. Paralysis or want of tone in the bladder prevents the thorough evacuation of its contents, and still more the expulsion of the fragments of stone. 2. _A good instrument_ should, as far as possible, combine strength with lightness. The curved portion of the fixed blade should be fenestrated to allow escape of the fragments and thorough closure of the instrument. The movable blade must be so arranged as to combine perfect ease of movement up and down in seeking for the stone, with a powerful, slow, and gradual approximation in crushing it. This can be managed by an ingenious arrangement, which leaves the movable blade under the control only of the operator's thumb till the stone is found, and yet, by touching a spring, gives him the advantage either of a fine screw or of a rack and pinion movement for crushing the stone. 3. _Operation._--The patient being prepared by a free evacuation of the bowels, and the urethra having been previously fairly dilated, he is asked to retain his urine as long as possible, or, if he cannot do so, a few ounces of tepid water may be injected per urethram. He is then laid on a sofa or table, the breech being well raised by pillows, the shoulders low, the thighs and knees bent up and separated. The instrument, well warmed and oiled, is then introduced with the blades closed. When fairly into the bladder the search for the stone begins. There are differences of opinion regarding the best method of fishing for the stone; great patience and gentleness, with a thorough previous acquaintance with bladder manipulation, are required, whichever method be chosen. The two chief methods may be described as the English and the French, the latter, Civiale's, being now used by Sir Henry Thompson, and other English operators. Briefly, the two are:-- (1.) _Heurteloup's and Sir B. C. Brodie's._--In this, after the instrument is fairly entered, its handle is elevated, thus depressing the curved extremity, the forceps are then opened, and, by being kept as low as possible in the bladder, it is hoped that the calculus will fall into the opened blades by its own weight. In this method the fundus is the scene of crushing, and there is a risk of injuring the sensitive neck of the bladder, especially at the moment of opening the blades.