PYRIFOR3IIS OBTURATOR INTERNUS. 



225 



Fig. 8f). 



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 separation 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. 



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

 from the anterior surface of the 

 sacrum, by little slips that are inter- 

 posed between the anterior sacral 

 foramina., It passes out of the pel- 

 vis, 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 the 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 gemel- 

 lus superior, ischiatic vessels and 

 nerves, and internal pudic vessels 

 and nerve. 



Immediately below the pyriformis is a small slip of muscle, the 

 gernellus superior (gemellus, double, twin) ; 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 superior is not 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 an- 

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



* The deep muscles of the gluteal region. 1. The external surface of the ilium. 2. 

 The posterior surface of the sacrum. 3. The posterior sacro-iliac ligaments. 4. The 

 tuberosity of the ischium. 5. The great or posterior sacro-ischiatic ligament. 6. The 

 lesser or anterior sacro-ischiatic ligament. 7. The trochanter major. 8. The gluteus 

 minimis. 9. The pyriformis. 10. The gcmellus superior. 11. The obturator inter- 

 ims muscle, passing out of the lesser sacro-ischiatic foramen. 12. The gemellus infe- 

 rior. 13. The quadratus femoris. 14. The upper part of the adductor magnus. 15. 

 The vastus externus. 16. The biceps. 17. The gracilis. 18. The semi-tendinosus. 



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