_The operation._--A semilunar incision is made transversely across the perineum, extending from a point midway between the right tuber ischii and the anus, upwards, crossing the raphe nearly an inch above the anus, and then curving downwards to a corresponding point on the opposite side. The skin, superficial fascia, and a few of the anterior fibres of the external sphincter, are thus divided, and the groove of the staff sought by the forefinger. The membranous portion of the urethra is then laid open in the middle line, and the beak of a double lithotome caché securely lodged in the groove. It is then pushed into the bladder with its concavity upwards, and when fairly in it is turned round, its blades protruded to the required extent, and withdrawn with its concavity downwards, thus dividing both lobes of the prostate in a direction downwards and outwards (Fig. XXIV. D D). The operation is finished in the usual manner. Though it is a comparatively easy operation, and theoretically may be proved to have many advantages, experience has shown that the results are not so favourable as those of the ordinary lateral operation. 2. _Buchanan's medio-lateral operation_ on a rectangular staff.--The staff is bent at a right angle three inches from the end, and deeply grooved on its left side. This is introduced into the urethra so that the angle projects the membranous portion of the urethra close to the apex of the prostate and the terminal straight portion enters the bladder parallel to the rectum. The angle projects in the perineum, so that the operator with his left forefinger in the rectum is enabled, by a stab with a long straight bistoury (held horizontally and with the cutting edge to the left side), at once to enter the groove, and, by following the groove, the bladder. Whenever the escape of urine shows that the bladder is fairly reached, the knife is withdrawn so as to make a lateral section of the prostate, and then, with the finger still in the rectum, to make an incision in the ischio-rectal fossa, of sufficient size to allow the stone to be easily withdrawn. The inventor claims for this method that it is easier, that there is less risk of hæmorrhage, wound of the rectum, and infiltration of urine. 3. _Allarton's operation of median lithotomy_ suits admirably for stones known to be small, but is quite unsuitable for large ones. Probably in most cases it should be superseded by lithotrity.