PELVIC APONEUROSIS. 177 



times called the recto-vesical fascia or recto-vesical aponeuro- 

 sis. The reflection of this fascia about the rectum, is consid- 

 ered by Mr. Tyrrel as consisting of two layers. One which he 

 calls the middle layer (see fig. 167,) passes between the base of 

 the bladder, and the anterior face of the rectum. The other 

 called by him the inferior layer, passes behind the rectum and 

 with the layer of the opposite side completely surrounds this 

 intestine. To the middle layer he has proposed to restrict the 

 term recto-vesical fascia ; but this name, it appears to me is too 

 commonly used in the more extended sense, to admit of this 

 limitation. 



— As the fascia of each side passes from the two pubic bones to 

 the bladder, there is formed in front two ligamentous bands, with 

 a small fascia between them, lined by the peritoneum. These 

 bands constitute the anterior ligaments of the bladder. 

 — Posteriorly tjiis fascia or aponeurosis is reflected backwards 

 from each side upon the front surface of the sacrum, where it 

 becomes thin and is finally lost. It passes in front of the sciatic 

 plexus of nerves, over which it sometimes forms a bow. 

 — Another bow formed by this aponeurosis has been carefully 

 described by Mr. Colles, the concavity of which looks up- 

 wards. The anterior end of this bow is fastened to the pubis 

 above the thyroid foramen ; the posterior to the ischium above 

 its spine. This bow is called from its shape semi-lunar. At 

 this point the pelvic aponeurosis splits into two layers, the inter- 

 nal one of which, or \\\e pelvic, has alone been described. The 

 other or outer one, is called the obturator, and passes directly 

 downwards, as seen in fig. 167, lining the inner surface of the 

 obturator internus muscle, and forming a sheath for the internal 

 pudic vessels and nerves. Between these two fascia from which 

 it partly has its origin, lies the levator ani muscle. The obtu- 

 rator, and levator ani muscles diverge below from each other, 

 forming thereby a. fossa opening downwards filled up with very 

 vascular fat, called the ischio-rectal fossa. At the point of di- 

 vergence, a thin process is sent off from the obturator fascia, 

 which lines the lower portion of the levator ani muscle, and is 

 continued on to the anus, this is sometimes called the anal fascia. 



