PELVIS 581 



from the anterior surface of the rectum, and still more later- 

 ally the apical part of the seminal vesicle lies on the levator 

 ani at the side of the rectum, while the lower part of the 

 ureter intervenes between the vesicle and the bladder wall. 



Dissection. The anterior part of the prostate was divided when the 

 urethra was opened. The dissector should now divide the posterior part in the 

 median plane. The rectum must then be divided in the median plane, and 

 afterwards the sacrum and coccyx must be divided vertically by a saw- 

 cut, to the left of the middle sacral artery. The separation of the two 

 halves of the pelvis from each other must be completed by the division of any 

 remaining soft parts with the knife. All the subsequent stages of dissection 

 and the examination of the relations of the viscera can be quite con- 

 veniently carried out on each side separately. 



Relations of Blood Vessels and Nerves to the Pelvic 

 Fascia. The dissector should again note that the blood 

 vessels of the pelvis are placed on the peritoneal surface of 

 the pelvic fascia. It follows, therefore, that all the branches 

 pierce the fascia as they pass to the viscera or as they pass 

 out of the pelvis, and they carry with them prolongations 

 of the fascia which blend with their sheaths. There is one 

 exception to this rule, viz. the obturator artery, which passes 

 over the upper border of the parietal pelvic fascia into the 

 obturator canal. The nerves lie outside the fascia, and, ivith 

 the exception of the obturator nerve^ those which are leav- 

 ing the pelvis do not require to pierce it, but the branches 

 which are to supply the viscera pass through its substance to 

 gain their terminations, and the obturator nerve pierces 

 it posteriorly to gain the interior of the pelvis. This differ- 

 ence in the nerves and blood vessels can be well studied 

 by looking at the fascia as it passes over the great sciatic 

 foramen. 



The relation of the pelvic blood vessels to the lining fascia 

 is a matter of some practical importance. The margins of 

 the apertures in the fascia through which the vessels pass are 

 usually strengthened by some encircling fibres ; still, a portion 

 of gut may make its way through one or other of the openings 

 in the fascia and form a hernia. Sciatic hernia consists of 

 a protrusion of the gut through the great sciatic notch. 

 The hernia may be situated either above or below the 

 piriformis. In the former case it escapes through the 

 aperture in the fascia made by the superior glutaeal artery, 

 and in the latter through the aperture for the inferior glutaeal 

 or the internal pudendal artery. 



i 37 a 



