230 MUSCLES OF THE LOWER LIMB. 



it from the upper margin of the capsule of the hip-joint. A synovial 

 bursa is interposed between the tendon and the trochanter. 



IMations. — Tlic anteiior border of the muscle is in contact with that of the 

 gluteus medius ; its deep surface with the cap.sule of the hip joint, the dorsum 

 iUi, and the posterior head of the rectiis femoris : its outer svu-face is covered 

 by the gluteus medius, gluteal vessels and nerves ; and its posterior border is 

 covered by the pyrifonnis muscle. 



Varieties. — This muscle may be divided into an anterior and a ^Dosterior part, 

 or it may send detached slips to the hip joint, to the pyrifonnis, to the gemellus 

 superior, or to the outer part of the origm of the vastus extemus (Macalister). 



The pyriformis muscle arises within the pelvis by three flesliy 

 digitations from the second, third, and fourth divisions of the sacrum, 

 between the anterior sacral foramina, slightly from the deep surface of 

 the iliac bone, near the sacro-sciatic notch, and from the sacro-sciatic 

 ligament. The muscle passes out of the pelvis by the great sacro- 

 sciatic notch, and is inserted by a rounded tendon into the upper 

 border of the great trochanter, being bound down for some distance 

 from the point of its final insertion to the subjacent tendon of the 

 obturator internus and gemelli muscles. 



lidatlons. — The pyi-iformis muscle, after escaping from the pelvis, is in contact 

 by its upper border with the gluteus medius and minimus, the gluteal vessels and 

 nerve intervening ; and by its lower border with the superior gemellus muscle, 

 the sciatic vessels and nerves, which emerge beneath it, lying between ; its outer 

 surface is covered by the gluteus maximus, and its deep surface is in contact with 

 the capsule of the hip joint. 



Varhth;f. — This muscle is frequently found to be pierced by the gi-eat sciatic 

 nerve or by its external popliteal branch, and is thus divided more or less com- 

 pletely into two parts. It may be united with the gluteus medius. superior 

 gemellus, or obturator intemus. It may have only one or two sacral attach- 

 ments, or again its tendon may be inserted into the hip joint. Its entire absence 

 has also been noted. 



The obturator interims muscle, in great part lodged witliin the 

 pelvis, arises Irom the deep surface of the obturator membrane ; from 

 the fil)rous arcli which completes the canal for the obturator vessels and 

 nerves; from the bone surrounding the obturator foramen, extending* 

 downwards to the outlet, backwards as far as the sciatic notch, and 

 upwards to the brim of the pelvis ; a few fibres also arise from the 

 obturator fascia, Avhich is in contact with the deep surface of the 

 muscle. Its fibres converging as they proceed backwards from this 

 origin, the muscle emerges from the pelvis by the small sacro-sciatic 

 foramen, gliding over the trochlear surface of the ischium, and is directed 

 outwards, to be inserted, in connection witli the gemelli, into the upper 

 part of the digital fossa of the great trochanter. The tendon, occupying 

 the surface of the muscle which is towaixls the bone, is i'olded together 

 into four or five plaits which lie side by side as they turn over the trochlear 

 groove : their motion in that groove is facilitated by a synovial bursa, 

 which is inflected over them, and by a thin coating of cartilage on the 

 trochlear surface of the bone. Another bursa, of much smaller size, 

 elongated and narrow, is placed between the tendon and the fibrous 

 capsule of the hip- joint. These bursaj are sometimes continuous with 

 one another 



Hclations. — The deep sui-face of the pelvic portion is in contact with the deep 

 pelvic fascia and near its lower border with the ^mdic vessels and nerve. The 

 outer sui-f ace is in contact with the bones and obtm-ator membrane. At its upper 



