202 SURGICAL ANATOMY OF 



two triangles, by a line passing from one tuberosity of 

 the ischium to the other, in front of the anus, and call- 

 ing all in front of it the perineum, and all behind it, the 

 anal, or ischio-rectal region. It is proposed to adopt 

 the latter method in this description, and it will be seen 

 that, although it may appear arbitrary as far as the su- 

 perficial layer of fascia is concerned, as the dissection 

 proceeds deeper towards the inner aspect of the pelvis, 

 the arrangement is a natural one, as adapting itself to 

 the special contents of each triangular space. The 

 boundaries of the anterior portion, which is convex in 

 the middle, owing to the position of the bulb of the 

 urethra, are below, a line passing horizontally in front 

 of the anus from one tuberosity of the ischium to the 

 other ; and laterally, the pubic rami, meeting at the 

 symphysis ; thus forming a triangular interspace, which 

 is itself divided by the median raphe into two equal 

 parts, the left being the one in which the lateral opera- 

 tion of lithotomy is performed, supposing the operator 

 to be right-handed. This raphe indicates the course 

 taken by the urethra, and is a most valuable landmark 

 in all operations about the perineum. The sides of this 

 triangular space are about three inches and a half long, 

 and about three inches across the base, and a line drawn 

 from the apex of the triangle to its base, about three 

 inches. 



Superficial Dissection of the Perineum. A staif having 

 been introduced into the bladder, and the hair shaved 

 off the nates, an incision is to be made through the in- 

 tegument in the middle line, a second at right angles to 

 it in front of the anus, and a third, parallel to the latter 

 across the base of the scrotum. The flaps thus formed 

 are to be reflected outwards, when the subcutaneous eel- 



