PELVIS 559 



parts of the ductus deferentes. The lateral borders of the 

 fold curve backwards to the sacrum, passing at some little 

 distance from the sides of the rectum. From the lower 

 surface of the sacro-genital fold the peritoneum passes to 

 the front of the rectum, on which it is reflected upwards to 

 the pelvic colon. Below the line of reflection from the sacro- 

 genital fold there is a part of the rectum entirely devoid of 

 any peritoneal covering. The part immediately above this is 

 covered only in front, but at a higher level the front and the 

 sides also are covered, and when the pelvic colon is reached 

 the peritoneum entirely surrounds that part of the gut and 

 attaches it to the posterior wall of the pelvis by a fold or 

 mesentery, the pelvic meso-colon. The hollow or pouch 

 between the sacro-genital fold in front and the rectum behind 

 is the recto-vesical or recto-genital excavation. 



The Peritoneal Fossae. rAs the peritoneum follows the 

 contours of the more projecting viscera, three hollows or 

 secondary pouches are formed on each side : an anterior 

 or paravesical, a middle or genital, and a posterior or pararectal. 

 The paravesical fossa is bounded medially by the bladder, 

 laterally by the pelvic wall, and posteriorly by a ridge of 

 peritoneum, caused by the ureter, which runs backwards and 

 outwards from the postero-lateral angle of the upper surface 

 of the bladder towards the hypogastric artery. Beneath the 

 floor of this fossa the ductus deferens runs medially towards 

 the genital fossa. The genital fossa lies between the ureteral 

 ridge and the margin of the sacro-genital fold ; and the para- 

 rectal fossa is between the sacro-genital fold and the side of 

 the rectum. The two pararectal fossae are continuous with 

 each other across the front of the rectum and form together 

 the recto-vesical excavation. When the rectum is distended 

 the peritoneum of the pararectal fossae is lifted up to cover 

 the expanding wall of the viscus, the fossae are obliterated, 

 and the posterior ends of the sacro-genital folds terminate 

 on, or in close relation with, the wall of the rectum. 

 When the bladder is distended the middle part of the sacro- 

 genital fold is also opened out to help to cover the upper 

 part of the fundus of the bladder, but the lateral parts 

 remain. If, however, the bladder and rectum are simultane- 

 ously distended the lateral parts of the sacro-genital fold 

 pass from the back of the bladder either to the rectum 

 or to the posterior wall of the pelvis close to the rectum, 



