chap, xvin.) THE PERINEUM. 389 



inches in front of the anus. The incision is carried 

 downwards and outwards into the left ischio-rectal 

 fossa, and ends at a point between the tuber ischii and 

 posterior part of the anus, and one-third nearer to the 

 tuberosity than to the gut. In the early part of this 

 incision the staff may just be touched, as it lies in the 

 membranous urethra, the incision becoming more and 

 more shallow as the knife is withdrawn. The parts cut 

 in the first incision are : (1) Skin and superficial fascia; 

 (2) transverse perineal muscle, artery and nerve; (3) the 

 lower edge of the anterior layer of the triangular 

 ligament ; (4) the external hoemorrhoidal vessels and 

 nerve. 



In the second incision the knife, guided by the fore- 

 finger of the left hand, is passed upwards behind the 

 triangular ligament, is engaged in the groove on the 

 staff as it lies in the membranous urethra, and then, 

 having its edge turned towards the left tuber ischii, is 

 steadily earned along the groove into the bladder. In 

 this incision the parts divided are: (1) Membranous and 

 prostatic portions of urethra ; (2) posterior layer of tri- 

 angular ligament; (3) compressor urethrse; (4) anterior 

 fibres of levator ani and left lateral lobe of prostate. 

 The finger is then introduced along the staff into the 

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

 inserted, the stone is extracted, traction being made in 

 the proper axis of the pelvis. 



Parts that may be wounded. (a) In the first in- 

 cision : (1) the bulb, or the artery to the bulb. These 

 parts can be avoided by commencing the incision well 

 behind the " central point," and by causing the 

 holder of the staff to draw it, the scrotum, and the 

 penis well up. The staff should be held as close 

 up under the pubes as possible. The bulb is very small 

 in children, large in adults, and largest in old men. 

 (2) The rectum may be cut if much distended, or if 

 the incision be made too vertical or carried too for 



