1. The perineum, where access is gained through the urethra, prostate, and neck of the bladder. 2. Above the pubes, where the portion of bladder not covered by peritoneum is opened from above. 3. From the rectum. 1. LITHOTOMY THROUGH THE PERINEUM, by far the most frequent position for the operation.--Very various methods for its performance have been devised, differing in the nature and shape of the instruments employed, the direction and size of the incisions, the nature of the wound; but all resemble each other in certain very cardinal and important particulars. Thus all agree that it is absolutely necessary to enter the bladder at _one_ spot--the neck of the bladder; and that to do this safely the urethra must be opened, and some instrument previously introduced by the urethra is to be used as a guide for the knife. But an instrument in the urethra and bladder is surrounded for at least an inch of its course by the prostate; and thus the knife, gorget, or finger, which, guided by the instrument in the urethra, is intended to cut or dilate the entrance to the bladder for the purpose of allowing the calculus to be removed, cannot do this without also cutting or dilating this prostate gland. Experience has proved that much of the success of the operation depends upon the position and amount of incision made in this prostate gland. But it might be asked, Why can we not enter the bladder by one side, avoiding altogether its neck and this prostate gland? For this, among other reasons, that the bladder normally contains, and so long as the patient lives must contain, a certain quantity of a very irritating fluid. It is surrounded by the loose areolar tissue of the pelvis, into which, if any of this fluid escapes, abcesses will form and death probably ensue; this result will almost certainly follow any opening made into the bladder except at one spot. This spot is the neck of the bladder. Why does urinary infiltration not occur there? Because the fascia of the pelvis (which when entire can resist infiltration) is prolonged forwards at the neck of the bladder, over the prostate (Fig. XXXIV. PF), for which it forms a very strong funnel-like sheath. So long as this sheath is not cut where it covers the sides of the prostate, urinary infiltration of the pelvis is impossible, the urine being carried forwards and fairly out of the pelvis in this urine-tight funnel. [Illustration: FIG. XXXIV.[150]] But it may now be said, If this be the case, we are very much limited in the size of the incision we may make into the bladder. We cannot remove a large stone, for the prostate ought not to be larger than a good-sized chestnut, and any cut we might make through a chestnut without cutting out of its side must be very small. Very true; but fortunately the sheath of the prostate, unlike the rind of the chestnut, is very freely dilatable, and will allow the passage of a very considerable stone.