DISSECTION OF THE PELVIS. 343 



111 the female the internal pudic teiininates in hsemon'hoidal, vulval", 

 and bulbous branches; and, instead of the vesico-prostatic, it gives off 

 the vaginal artery, Avhich is expended in the bladder, vagina, and cervix 

 uteri, anastomosing with branches of the uterine artery. 



The Umbilical or Hypogastric Artery. In the adult (Plate 46) this 

 is a comparatively small vessel arising from the internal pudic near its 

 root. It is pervious only in the first few inches of its course, giving off 

 a few twigs to the bladder, and being then continued as a solid cord at 

 the free edge of the lateral ligament of the bladder. In the foetus, 

 however, it is of great size, and carries the foetal blood to the placenta to 

 be purified. 



The Internal Pudic Vein runs in company with the artery. It 

 receives branches corresponding to those of the artery, and terminates in 

 the internal iliac vein. 



The Pudic Nerve is derived from the 3rd sacral. Descending on the 

 inner surface of the sacro-sciatic ligament, it crosses the internal pudic 

 vessels superficially at the small sacro-sciatic foramen. Here it turns 

 slightly inwards, and disappears beneath the ischio-urethral muscle. 

 Having gained the lower face of the urethra, it turns round the ischial 

 arch, and is continued as the dorsal nerve of the penis. Before leaving 

 the pelvis, it detaches a perinceo-anal branch, which gives twigs to the 

 muscles of the urethra and penis, and hsemorrhoidal branches that pass 

 upwards on the rectum to reach the anus, some of them appearing to 

 terminate in the sphincter. These latter branches are crossed by de- 

 scending branches from the hsemorrhoidal nerve. 



The lower posterior gluteal nerve (Plate 16) gives fibres to both the 

 trunk of the pudic nerve and its perinaeo-anal branch, and in some cases 

 the latter derives the majority of its fibres from this source. 



In the female the pudic nerve terminates in branches to the labia, 

 clitoris, and constrictor muscles of the vulva. 



The Hemorrhoidal Nerve is derived mainly from the 4th sacral. It 

 descends on the inner face of the sacro-sciatic ligament, and (for a short 

 distance) the compressor coccygis muscle. It supplies a twig to that 

 muscle, and then penetrates it, or emerges between it and the retractor 

 ani. It then divides into branches for the retractor and sphincter 

 muscles of the anus, and for the skin of the periuEeum. 



The Retractor Anl This muscle is described with the perinseum 

 (page 276), but it is here exposed in the whole of its extent. 



The Compressor Coccygis (Fig. 48) arises from the inner surface of the 

 sacro-sciatic ligament, over the superior ischiatic spine. Passing back- 

 wards and upwards, it is inserted into the last sacral and first two coccy- 

 geal vertebrae. By its inner face it is related to the rectum, except close 

 to its insertion, where the edge of the depressor of the tail intervenes. 



Action. — Acting with the opposite muscle, it forcibly depresses the 



