Internal Pit die Artery 441 



dorsal vein. Beneath these muscles the triangular ligament stretches 

 across the sub-pubic arch. In lateral lithotomy, the surgeon, being 

 right-handed, plunges his knife through the muscular triangle on the 

 left side of the patient. 



The superficial perineal vessels and nerves (from the internal 

 pudics) pass forwards over the triangle, getting beneath the deep layer 

 of the superficial fascia just where it is turning down to the base of the 

 triangular ligament. 



To expose the triangular ligament in the dissection of the peri- 

 neum, the erector penis and the crus must be detached from the pubic 

 arch, and the transverse muscle removed ; and not only must the 

 accelerator urinas be dissected off, but the hinder end of the corpus 

 spongiosum should be also cut away, and with it, of course, the bulbous 

 part of the urethra. The chief use of the ligament is to steady 

 and support the urethra as it curves below the pubic symphysis. The 

 better to do this, it is composed of two aponeurotic sheets, which, 

 separated from each other by an interval of about one-third of an 

 inch, descend to blend with each other, and with the deep layer of the 

 superficial fascia, at the base of the triangle. The deeper layer of the 

 triangular ligament is joined also by the recto-vesical fascia. 



The urethra pierces the two layers of the ligament about one inch 

 below the symphysis ; when running between them it is surrounded 

 by a striated sphincter, the compressor urethrse. The beak of a 

 catheter is apt to catch against the ligament unless the handle be well 

 depressed. Closer beneath the symphysis the dorsal vein of the 

 penis runs through the layers to join the prostatic plexus. 



The endings of the internal pudic artery and nerve ascend between 

 the two layers of the ligament towards the dorsum of the penis ; they 

 have entered the ligament near its base, and close against the ischial 

 ramus. The short piece of the urethra enclosed in the triangular 

 ligament is the membranous part, and close below it are Cowper's 

 glands -(v. p. 413). The triangular ligament is very strong, and pre- 

 vents extravasated urine, and the contents of a perineal abscess, pass- 

 ing backwards to enter the pelvis. In addition to the parts already 

 enumerated between its two layers are the sub-pubic ligament ; a 

 short branch of the internal pudic artery to the bulb of the urethra, 

 and sometimes another transverse (deep) perineal muscle. 



Cowper's glands are about the size of a pea ; they are lobulated, 

 and their ducts pass through the anterior layer of the triangular liga- 

 ment to open on to the floor of the bulbous part of the urethra, as 

 already noted, on p. 417. 



The internal pudic artery is one of the terminal trunks of the 

 anterior divisions of the internal iliac ; leaving the pelvis below the 

 pyriformis, it winds round the ischial spine into the ischio-rectal 

 fossa, passing through the small sacro-sciatic foramen. In the fossa 

 it lies in a tube of the obturator fascia, an inch or more above the tuber 



