176 SUPERIOR PERINEAL FASCIA. 



3. The superior perineal fascia or pelvic aponeurosis, 

 is but an extension of the fascia covering the iliacus internus 

 muscle, (fascia iliacd) that passes beneath the external iliac 

 vessels, turns over the brim of the pelvis to which it becomes 



Fig. 167.* 



attached, and then dips down to line the sides and bottom 

 of the pelvic cavity. The rectum and bladder having tubular 

 outlets which open inferiorly, the fascia cannot pass as a level 

 sheet across the bottom of the cavity ; but where it encounters 

 the rectum, and the bladder with its adherent prostate, it 

 mounts up upon the sides of these organs, giving them an 

 aponeurotic coat. Hence the layer at the bottom of the pelvic 

 cavity which constitutes the superior perineal fascia, is some- 



* A transverse section of the pelvis, showing the distribution of the pelvic 

 fascia. 1. The bladder. 2. The vesiculae seminales divided across. 3. The 

 rectum. 4. The iliac fascia covering in the iliacus and psoas muscles (5) ; and 

 forming a sheath for the external iliac vessels (G). 7. The anterior crural nerve 

 excluded from the sheath. 8. The pelvic fascia.. 9. Its ascending layer, form- 

 ing the lateral ligament of the bladder of one side, and a sheath to the vesical 

 plexus of veins. 10. The recto-vesical fascia of Mr. Tyrrel formed by the 

 middle layer. 11. The inferior layer surrounding the rectum and meeting at 

 the middle line with the fascia of the opposite side. 12. The levator ani mus- 

 cle. 13. The obturator internus. muscle, covered in by the obturator fascia, 

 which also forms a sheath for the internal pudic vessels and nerve (14). 15. 

 The layer of fascia which invests the under surface of the levator ani muscle, 

 the anal fascia. 



