396 



DISSECTION OF THE PERINEUM. 



the offsets of the perinaeal nerve to the deep muscles and the urethra, with 

 the vessels accompanying them. 



The TRIANGULAR LIGAMENT OF THE URETHRA (fig. 131, C ) (perina?al 



aponeurosis) occupies the anterior part of the pubic arch, and supports the 

 urethra! canal. The ligament is triangular in form, with its base below ; 

 and it is about one inch and a half in depth. 



Fig. 131. 



DEEP DISSECTION OF THE PERINJECM. (Illustrations of Dissections.) 



Muscles : 



A. Erector penis. 



B. Ejaculator nrinje, cut. 

 c. Triangular ligament. 

 B. External sphincter. 



F. Bulbous part of the urethra. 



e. Levator ani. 



H. Deep transverse. 



i. Constrictor urethra. 



K. Cms penis, cut. 



Arteries : 



a. Pudic, in the triangular ligament. 

 6. Dorsal of penis. 



c. Cavernous. 



d. Deep muscular and nrethral branch. 

 Nerves : 



1. Pndic trunk. 



2. Deep perinasal or muscular branch. 



3. Dorsal of the penis. 



On each side it is fixed to the pubic arch beneath the crus penis. Its 

 apex is connected with the symphysis pubis. Its base is turned towards 

 the rectum, and is partly attached and partly free; in the middle line it is 

 connected with the central point of the perinaeum, whilst laterally it is 

 s'oped towards the bone, so that it is less deep at the centre than at the 

 sides: connected with the lower border is a thin fascia which covers the 

 surface of the levator ani muscle in the ischio-rectal fossa. Superficial to 

 it are the muscles in the anterior half of the perinaeal space ; and the super- 

 ficial fascia is united to it near the lower border. 



The ligament is composed of two layers of membrane (anterior and pos- 

 terior) which are united below. The posterior layer is derived from the 

 recto-vesical fascia. The anterior is a separate membrane, formed chiefly 

 of transverse fibres, but it is so thin as to allow the vessels and the mus- 

 cular fibres to be seen through it. 



