248 



DISSECTION OF THE PERINEUM. 



in litho- 

 tomy. 



Perineal 

 nerve has 



cutaneous, 

 muscular, 



and genital 

 branches. 



Dissection 



posterior part of this space during the deeper incisions in the lateral 

 operation of lithotomy will divide the transverse muscle and artery, 

 and probably the superficial perineal vessels and nerves. 



The PERINEAL BRANCH OF THE PUDic NERVE (p. 242) breaks 

 up in the fore part of the ischio-rectal fossa into superficial and deep 

 branches. Its two superficial offsets have been followed to the 

 scrotum (p. 246). The deep branches are muscular to the fore parts 

 of the external sphincter and levator ani, to the transversus perinei, 

 erector penis, and ejaculator urinse, and the nerve to the bulb, a long 

 slender branch, which pierces the last muscle and, dividing into 

 filaments, enters the hinder portion of the corpus spongiosum. 



Dissection (fig. 94). For the display of the triangular ligament, 

 of triangular ,, , . 1-1' r. . i , 



ligament. the muscles and the cms penis, which are superficial to it, are to be 

 detached on the left side in the following way ; the ejaculator urinae 

 is to be removed completely from the corpus spongiosum and the 

 surface of the ligament, and the erector muscle from the cms of the 

 penis. Next, the crus penis is to be detached from the bone ; but 

 this must be done with care so as not to cut the triangular ligament 

 nor to injure the terminal branches of the pudic artery and the dorsal 

 nerve of the penis near the pubic ramus. 



The TRIANGULAR LIGAMENT OF THE URETHRA (deep perineal 

 aponeurosis ; fig. 94, c) occupies the anterior part of the sub-pubic 

 arch, and is about one inch and a half in depth in the middle line. 



On each side it is fixed to the pubic and ischial rami beneath the 

 crus penis. Its base is turned towards the rectum, and in the 

 middle line is united with the central point of the perineum ; while 

 laterally it is free and sloped towards the bone, so that the ligament 

 is deeper at the sides than in the centre. Superficial to it are the 

 bulb of the corpus spongiosum and the crura of the penis, with the 

 muscles of the anterior half of the perineal space ; and the super- 

 ficial fascia joins it along the hinder border. From its deep surface 

 some fibres of the levator ani arise ; and the thin anal fascia is con- 

 tinued backwards from the ligament over that muscle in the ischio- 

 rectal fossa. 



The ligament is composed of two layers of membrane (superior and 

 inferior) which are united along the base. The superior layer is 

 derived from the fascia of the pelvis. The inferior layer (now seen) 

 is a separate membrane, formed chiefly of transverse fibres ; but it 

 is so thin as to allow the vessels and the muscular fibres to be seen 

 through it. 



Perforating the inferior layer of the ligament, about one inch from 

 the symphysis pubis, is the canal of the urethra ; but the margin of 

 the opening giving passage to that tube is blended with the tissue 

 of the corpus spongiosum. Nearer the symphysis, and close to the 

 bone on each side, the terminal part of the pudic artery and the 

 dorsal nerve of the penis (b and 3) perforate the ligament by separate 

 apertures. 



Between the layers of the ligament are contained the membranous 

 part of the urethra, the constrictor urethrse muscle, Cowper's glands, 



Triangular 

 ligament 

 of urethra 



attach- 

 ments, 



and rela- 

 tions ; 



consists of 

 two strata : 



apertures in 

 it for 

 urethra, 



for arteries 

 and nerves 

 of penis ; 



parts 



between 



layers. 



