The Lower Extremity and Pelvis 131 



Poupart's and edge of Gimbernat's ligament, and directly continuous behind with the 

 sheet that covers the iliac fossa. The Psoas parvus is inserted into the iliac fascia, 

 spreading out in a fan-shaped aponeurosis, of which the fibres can be traced as far out 

 as the outer half of Poupart's ligament, into the back wall of the femoral sheath, and 

 to the attachment of the fascia on the ilio-pectineal line. This last-mentioned place 

 of insertion of the tendon receives a strong slip, and there is frequently a secondary 

 ridge (ps.p),on the line opposite the ilio-pectineal eminence, that marks its attachment. 

 The pelvic surface can be divided into two descriptive areas by the ilio-pectineal 

 line. The upper of these forms the bony floor of the iliac fossa, and has just been 

 described. The iliac fascia makes a common covering for Psoas and Iliacus and is 

 attached to the ilio-pectineal line internal to and behind the Psoas. 



The lower or true pelvic surface (Fig. in) is enlarged by the presence of the 

 obturator membrane in the recent state, and the Obturator internus has an extensive 

 origin (No. 2 in Fig. in) from this membrane and from the bone as far up as the lower 

 sacro-iliac ligaments. From this origin the fibres converge on the lesser sciatic notch, 

 where they form a group of tendons that play round the notch on a cartilage-covered 

 surface lined by a bursa. It is therefore evident that the area of bone (A) between 

 the muscle origin and the notch is covered by the muscle that plays over it. 



In front of the muscle and above it a surface of bone (B) is left exposed. This is 

 covered by peritoneum, but under the peritoneum it is crossed by the obliterated hypo- 

 gastric artery (hyp.), the vas deferens or round ligament (v.d.), and further back may 

 have some relation to the external iliac vein (V.). Below the vein, the obturator nerve 

 (O.N.) runs to the top of the foramen and is joined by the vessels. 



To understand the remaining relations and attachments it is necessary to follow 

 the disposition of the pelvic fascia on the bone to some extent. 



The Obturator internus is covered by the parietal fascia of the pelvis which is 

 attached all round its pelvic surface : in No. 2, it is represented by the fine black line 

 pp, which is seen practically to map out the upper and front margins of the muscle 

 origin. At x it is continuous with the iliac fascia with some slight attachment to the 

 bone, and at y it runs into the ligaments. Along the front border of the great sciatic 

 notch it is continuous with the fascia covering Pyriformis with some slight attachment 

 to the bone : this is shown at xx in this drawing and in No. 3, where the fasciae are 

 represented in situ. The two fasciae separate at the ischial spine : pp is continued 

 along the front of the base of the spine and is carried from its lower border across the 

 notch and tendon to the top of the tuberosity by attachment along the lower part of 

 the lesser sciatic ligament and from this to the front border of the greater ligament. It 

 is now attached to the falciform extension of the greater ligament, and is thus carried 

 to the pubic ramus, where it again closely follows the muscle origin, reaching with it 

 the upper border (m) of the obturator membrane. 



When this parietal fascia is in position the bone is left uncovered in the area B, 

 while the spine of the ischium projects behind and between the fascia and that cover- 

 ing Pyriformis. The muscular floor of the pelvis is attached to these two bony surfaces 

 that is, to the lower and front part of the bone above and in front of the Obturator 

 and to the spine of the ischium, and between these points it arises from the parietal 

 fascia in a line connecting them. 



The floor is formed mainly by Levator ani, which has therefore a marking on 

 the back of the pubic body, but the back portion of the sheet is the Coccygeus : this, 

 then, arises from the ischial spine in addition to the hinder fibres of the Levator, and 

 as its back and upper fibres are converted into the lesser ligament, this structure is 

 attached to the tip of the spine and is in the plane of the pelvic floor. 



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