THE PELVIC FASCIA. 



379 



should proceed cautiously. By this proceeding the membrane is 

 dissected in its upper half, or as low as the situation of the portion 

 (Yrrto-vesical) which is directed inwards to the viscera. 



To display the lower half, the student must raise the outlet of 

 the pelvis ; and, should the perineum be undissected, the fat must and the 

 be taken from the ischio-rectal fossa. The lower part of the pelvic 



gsn 



la 



FIG. 142. DISSECTION OF THE PELVIC FASCIA (DRAWN BY C. F. BEADLES). 



the levator ani, showing through the 

 obturator fascia. 



/ py. Fascia of the pyriformis. 



s g n. Superior gluteal nerve. 



g a. Gluteal artery. 



py. Pyriformis muscle. 



y s n. Great sciatic nerve. 



s a. Sciatic artery. 



p r n. Pudic vessels and nerve, 

 entering the sheath in the obturator 

 fascia. 



g s s I. Great sacro-sciatic ligament. 



uc. Acetabulum. 



c. Aperture of canal for obturator 

 vessels and nerves, bounded below by 

 o ra. the upper end of the obturator 

 membrane, the greater part of which 

 has been taken away. Below these, 

 the fascia of the obturator interims 

 is exposed by the removal of a por- 

 tion of the bone and the muscle. 



* Line along which the recto- 

 vesical fascia is given off from the 

 inner side of the obturator fascia. 



1 a. Tendinous fibres of origin of 



fascia will now appear on the outer side of that fossa, as it covers 

 the obturator muscle. 



To see the outer surface of the fascia (fig. 142), the obturator from outer 

 externus muscle and the obturator membrane should now be Slde ' 

 removed, with the exception of a small portion of the latter at the 



