OBTURATOR INTERNUS. 245 



This muscle should now be removed from its origin and turned down, 

 so as to expose the next, which is situated beneath it. 



The GLUTEUS MINIMUS is a radiated muscle, arising from the surface 

 of the dorsum ilii, between the superior and inferior curved lines ; its 

 fibres converge to the anterior border of the trochanter major, into which 

 it is inserted by means of a rounded tendon. There is no distinct line of 

 iseparation between the gluteus medius and minimus anteriorly/ 



Relations. By its superficial surface with the gluteus medius, and 

 gluteal vessels. By its deep surface with the surface of the ilium, the 

 long tendon of the rectus femoris, and the capsule of the hip joint. A 

 bursa is interposed between the tendon of the muscle and the trochanter. 



The PYRIFORMIS muscle (pyrum, a pear, i. e. pear-shaped) arises from 

 the anterior surface of the sacrum, by little slips that are interposed be- 

 tween the first and fourth anterior sacral foramina, and from the adjoining 

 surface of the ilium. It passes out of the pelvis, through the great sacro- 

 ischiatic foramen, and is inserted by a rounded tendon into the trochanteric 

 fossa of the femur. 



Relations. By its superficial or external surface with the sacrum and 

 gluteus maximus. By its deep or pelvic surface with the rectum, the 

 sacral plexus of nerves, the branches of tne internal iliac artery, the great 

 sacro-ischiatic notch, and the capsule of the hip joint. By its upper border 

 with the gluteus medius and gluteal vessels and nerves. By its lower 

 border with the gemellus superior, ischiatic vessels and nerves, and internal 

 pudic vessels and nerve. 



The GEMELLUS SUPERIOR (gemellus, double, twin) is.,a small slip of 

 muscle, situated immediately below the pyriformis ; it arises from the 

 spine of the, ischium, and is inserted into the upper border of the tendon 

 of the obturator internus, and into the trochanteric fossa of the femur. 

 The gemellus s^iperloiFl^rTot unfrequently wanting. 



Relations. By its superficial surface with the gluteus maximus, the 

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

 deep surface with the pelvis, and capsule of the hip joint. 



The OBTURATOR INTERNUS arises from the inner surface of the anterior 

 wall of the pelvis, being attached to the margin of bone around the obtu- 

 rator 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 ten- 

 don, and appear to be auxiliaries or superadded portions of the obturator 

 internus. 



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 maxi- 

 mus, 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, ihe external surface of 

 the pelvis, and the capsular ligament of the hip joint. By its upper border \ 

 within the pelv'.s, with the obturator vessels and nerve : externally to the 



