chap, xviii.j LITHOTOMY. 391 



the knife should hit the instrument as near as possible 

 to the apex of the prostate. As the knife is withdrawn, 

 the whole of the membranous urethra is incised, and 

 a wound made in the median raphe of about one inch 

 and a quarter in length. The incision is made by 

 cutting upwards. A probe is then introduced into the 

 bladder, and, the staff being removed, the finger is 

 passed into that viscus by steady dilatation of the 

 parts, with some laceration of the prostate. The object 

 in this operation is to enter the bladder with the least 

 amount of cutting, and by dilatation rather than 

 incision. 



Parts divided. (1) Skin and superficial fascia ; 

 (2) sphincter ani ; (3) central point of perineum ; (4) 

 lower border of triangular ligament ; (5) whole 

 length of membranous uretlira ; (6) compressor 

 urethra. 



Advantages. (1) The bleeding is much less than 

 in the lateral operation, the slight vascularity of the 

 raphe being well known. (2) The pelvic fascia is much 

 less likely to be wounded if the bladder be entered by 

 dilatation rather than by incision, as in the lateral 

 procedure. 



Disadvantages. (1) The bulb is in great risk of 

 being wounded. It must, however, be noted that 

 wounds of the bulb in the middle line do not bleed 

 readily, as a rule. (2) The amount of space obtained 

 for the removal of the stone is very slight. (3) In 

 children the operation in its integrity is scarcely pos- 

 sible, since the prostate is quite rudimentary, and the 

 .slight attachments of the parts are such, that, in using 

 forcible dilatation, the bladder may readily be torn 

 from the urethra. If the incision be made upwards, 

 and one finger be retained in the rectum, the risk of 

 wounding the gut is not great. 



In lithotomy, and in other operations for reaching 

 the neck of the bladder through the perineum, it 



