254 MUSCLES OF THE GLUTEAL REGION. 



ischiatic vessels and nerves, and internal pudic vessels and nerve. By 

 its deep surface with the pelvis, and capsule of the hip-joint t 



The OBTURATOR INTERNUS arises from the inner surface of the an- 

 terior wall of the pelvis, being attached to the margin of bone around the 

 obturator foramen, and to the obturator membrane. It passes out of 

 the pelvis through the lesser sacro-ischiatic foramen, and is inserted by 

 a flattened tendon into the trochanteric fossa of the femur. The lesser 

 sacro-ischiatic notch, over which this muscle plays as through a pulley, 

 is faced with cartilage, and provided with a synovial bursa to facilitate 

 its movements. The tendon of the obturator is supported on each side 

 by the two gemelli muscles (hence their names), which are inserted 

 into the sides of the tendon, and appear to be auxiliaries or superadded 

 portions of the obturator intemus. 



Relations. By its superficial or posterior surface with the internal 

 pudic vessels and nerve, the obturator fascia, which separates it from 

 the levator ani and viscera of the pelvis, the sacro-ischiatic ligaments, 

 gluteus maximus, and ischiatic vessels and nerves. By its deep or 

 anterior surface with the obturator membrane and the margin of bone 

 surrounding it, the cartilaginous pulley of the lesser ischiatic foramen, 

 the external surface of the pelvis, and the capsular ligament of the 

 hip-joint. By its upper border, within the pelvis, with the obturator 

 vessels and nerve ; externally to the pelvis, with the gemellus superior. 

 By its lower border with the gemellus inferior. 



The GEMELLUS INFERIOR arises from the posterior point of the 

 tuberosity of the ischium, and is inserted into the lower border of the 

 tendon of the obturator internus, and into the trochanteric fossa of the 

 femur. 



Relations. By its superficial surface with the gluteus maximus, 

 and ischiatic vessels and nerves. By its deep surface with the ex- 

 ternal surface of the pelvis, and capsule of the hip-joint. By its 

 upper border with the tendon of the obturator internus. By its 

 lower border with the tendon of the obturator externus and quadratus 

 femoris. 



In this region the tendon only of the obturator externus can be 

 seen, situated deeply between the gemellus inferior and the upper 

 border of the quadratus femoris. To expose this muscle fully, it is 

 necessary to dissect it from the anterior part of the thigh, after the re- 

 moval of the pectineus, adductor longus and adductor brevis muscles. 



The OBTURATOR EXTERNUS muscle (obturare, to stop up) arises 

 from the obturator membrane, and from the surface of bone immedi- 

 diately surrounding it anteriorly, viz. from the ramus of the os pubis 

 and ischium : its tendon passes behind the neck of the femur, to be in- 

 serted with the external rotator muscles, into the trochanteric fossa of 

 the femur. 



Relations. By its superficial or anterior surface with the tendon 

 of the psoas and iliacus, pectineus, adductor brevis and magnus, the 

 obturator vessels and nerve. By its deep or posterior surface with 

 the obturator membrane and the margin of bone which surrounds 



