500 DISSECTION OF THE PELVIS. 



The PELVIC FASCIA is a thin membrane in close contact with the 

 obturator muscle, and is fixed to the bone around the attachment of the 

 fleshy fibres, so that it might be called the sj ecial fascia (obturator) of that 

 muscle. 



Superiorly it is fixed into the brim of the pelvis for a short distance at 

 the lateral aspect of the cavity. In front of that spot it does not extend 

 so high as the brim, but is inserted into the bone around the attachment 

 of the muscle, except opposite the hole for the obturator vessels and nerve, 

 where it is united with the obturator membrane. Inferiorly the fascia is 

 attached to the hip bone along the side of the pubic arch, and to the 

 margin of the great sacrosciatic ligament where the obturator internus 

 issues from the pelvis. 



The outer surface of the fascia is in contact with the obturator muscle. 

 The inner surface corresponds above with the cavity of the pelvis, and 

 below, with the ischio-rectal fossa. With this surface the thin membrane 

 (recto-vesical) supporting the viscera of the pelvis is united ; the place of 

 union being indicated, on looking into the pelvis, by a whitish line near 

 to, and on a level with the ischial spine. At the posterior border of the 

 obturator muscle the fascia is joined by a thin membrane (fascia of the 

 pyriformis) which covers the pyriformis muscle and the sacral plexus, but 

 is beneath the iliac vessels by branches of which it is perforated. 



The recto-vesical fascia may be now seen in part ; but it will be better 

 displayed after the hip bone has been taken away. 



Dissection. To obtain a side view of the pelvis it will be necessary to 

 detach the left innominate bone. The pelvic fascia is first to be separated 

 from the bone and the obturator muscle. The innominate bone is next to 

 be sawn through, in front, rather external to the symphysis, and, behind, 

 at the articulation with the sacrum. After the bone has been pulled some- 

 what away from the rest of the pelvis, the ischial spine with the recto- 

 vesical fascia attached to it may be cut off with a bone-forceps ; and the 

 rest of the bone may be then removed by cutting through the pyriformis 

 muscle, the vessels and nerves passing through the sacro-sciatic notch, and 

 any other structure that may retain it. 



A block is afterwards to be placed beneath the pelvis. The bladder is 

 to be moderately distended with air through the ureter, and the urethra 

 is to be tied. Some tow is to be introduced into the rectum, also into the 

 vagina if it is a female pelvis ; and a small piece is to be placed in the 

 pouch of peritoneum between the bladder and the rectum. After the 

 viscera are thus made prominent, the ischial spine and the recto-vesical 

 fascia should be raised with hooks whilst the levator ani and coccygeus 

 muscles below it are cleaned. 



Parts closing the pelvis below. In addition to the recto-vesical fascia, 

 the following parts close the pelvic cavity on each side, between the sacrum 

 and the pubic symphysis. 



Behind, the student will meet with the pyriformis passing through the 

 great sacio-sciatic notch, with the gluteal vessels and nerve above it. 

 Next comes the coccygeus muscle, c, on the small sacro-sciatic ligament, 

 between the ischial spine and the coccyx: one border of the muscle 

 reaches towards the pyriformis, the other to the levator ani ; and between 

 its hinder border and the pyriformis lie the sacral plexus of nerves (*), and 

 the sciatic and pudic vessels. 



The greater part of the rest of the pelvic outlet is closed by the levator 

 arii, D, which extends forwards from the coccygeus to the symphysis pubis. 



