THE PERINEUM, MALE. 399 



lip of the tuberosity of the ischium, blending with the falci- 

 form extension of the great sacrosciatic ligament ; behind, 

 about the margin of the great sacrosciatic notch and to the 

 front of the articular surface for the sacrum, and continuous 

 above with the posterior end of the iliopectineal line. By 

 its attachment to the great sacrosciatic ligament the fascia 

 is carried over the lesser sacrosciatic foramen ; underneath 

 the ligament an extension of the fascia is prolonged out- 

 ward, with the obturator internus muscle, into the gluteal 

 region. 



The obturator fascia is continuous behind with the thin 

 membrane covering the pyriformis muscle ; at its anterior 

 part it is pierced by the obturator nerve and vessels. It is 

 crossed obliquely from above downward by the line of at- 

 tachment of the recto vesical fascia, the so-called " white 

 line," which curves downward and backward from the inner 

 and upper surface of the pubes across the middle of the 

 obturator foramen and ends at the base of the spine of the 

 ischium. The obturator fascia above the " white line " is 

 within the pelvic portion of the abdominal cavity, and is 

 covered by peritoneum ; the portion below is extrapelvic 

 and belongs to the perineum. This perineal or anal portion 

 furnishes a canal (of Alcock) through which the pudic 

 vessels pass. 



The Pyriformis Fascia. Fig. 113. 



This is a thin membrane covering the muscle and sciatic 

 plexus of nerves. It is adherent about the origin of the 

 pyriformis and blends in front with the obturator and recto- 

 vesical fasciae. 



The Rectovesical Fascia. Fig. 113. Diags. 26, 27, 28. 



This may be said to come off the inner surface of 



the obturator fascia along a line reaching from the inner, 



