THE PELVIS. 275 



and pushed the same before themselves. In the pelvis, the bladder, rectum, and 

 uterus grew up and developed behind the peritoneum ; hence, not only are these 

 three structures behind the peritoneum, but all their adnexal parts as well ; they 

 are held in position more or less by the peritoneum, and those processes having 

 one end on the organ and the other fixed to a wall are called the peritoneal 

 ligaments of these organs. Inflate the bladder, and see, posteriorly, two folds 

 extending from the rectum to the bladder ; also a fold on each side from the iliac 

 fossa to the side of the bladder. The plica urachi is the superior ligament of the 

 bladder. The peritoneal ligaments of the bladder are tivo posterior, two lateral^ 

 and one superior. 



The Rectum. -The rectum begins at the pelvic brim, opposite the left sacro- 

 iliac synchondrosis. You will ligate and cut the same at this point, leaving the 

 sigmoid in situ. Notice that the upper part of the rectum has a fold of peri- 

 toneum the meso-rectum. The next stage of the rectum is partially covered 

 by peritoneum, like the descending colon. The lower part of the rectum, one 

 and one-half inches in length, and extending from the tip of the coccyx to the 

 anus, has no peritoneum, as you will see on the cadaver. Now search beside 

 the rectum and bladder and you will find the pelvic plexus of sympathetic 

 nerves, which supplies all the viscera in the pelvis. Here, as elsewhere, the 

 nerves accompany the arteries to the parts and take the same name. 



The pelvic fascia is the lower condensed layer of the subperitoneal connec- 

 tive tissue. It takes the following different names : iliac, obturator, recto-vesical,. 

 pubo-prostatic, anal, white line, Alcock's canal according to its location. The 

 white line you will see extending from the ischial spine to the pubic bone, one 

 inch below the subpubic arch. It is a split in the obturator fascia, from which 

 split arises the levator ani muscle. (Fig. 192.) The anal fascia covers the under 

 surface of the levator ani muscle. The recto-vesical fascia extends across the 

 upper surface of the levator ani muscle, investing the rectum and bladder. It 

 also extends from the pubes to the neck of the bladder and prostate, under the 

 name of pubo-prostatic. Demonstrate all these on the cadaver. 



The iliac fascia covers the iliacus muscle, passes out of the pelvis behind 

 the femoral vessels, and unites with the transversalis fascia by the side of the 

 femoral vessels to form the femoral sheath, as described on page 235. 



The obturator fascia covers the obturator internus muscle and delaminates 

 to form the wJiite line. (Fig. 192.) 



Relations of the Psoas Magnus Muscle. (i) Lying on the muscle you see 

 the psoas parvus ; (2) to the outer side, see the iliacus muscle and the anterior 

 crural nerve ; (3) to the inner side, skirting the pelvic brim, the common and exter- 

 nal iliac arteries are seen ; (4) to the inner side, and one-half of an inch below the 

 pelvic brim, see the obturator nerve and vessels ; (5) emerging from the front sur- 

 face of the middle third of the muscle, see the external cutaneous nerve ; (6) to 

 the inner side, between the muscle and the common iliac artery, see the genito- 

 crural nerve ; (7) to the outer side of the muscle, above, see the last thoracic, the 

 ilio-kv pogastric , and the ilio-fnguinal nerves ; (8) in the substance of the muscle, 

 this having been detached and removed piecemeal with the forceps from within 

 outward, see the lumbar plexus, giving off the following branches. 



Branches of the Lumbar Plexus (Fig. 190). Dissection : 



1. I lio-Jiy pogastric, to the skin over the gluteus maximus and over the hypo- 

 gastrium ; lies between the internal oblique and transversalis ; communicates 

 with the last dorsal. The hypogastric branch pierces the aponeurosis of the 

 external oblique muscle one inch above the external abdominal ring, and is dis- 

 tributed to the skin over the region of the bladder. 



2. Ilio-inguinal, crosses the quadratus and iliac muscles, pierces the trans- 

 versalis, lies between the internal oblique and transversalis, supplies the internal 



