614 A MANUAL OF ANATOMY. 



funda (below), the external circumflex, and the internal 

 circumflex upon the outer and inner sides of the femur. 

 This arrangement of. communicating branches constitutes 

 the " crucial anastomosis." The student must not expect 

 to find the inosculating branches forming any well defined 

 "cross." However, as one artery (the sciatic) is above, 

 another (first perforating) is below, and two others upon 

 either side (the external and internal circumflex) a some- 

 what "cross-shaped" anastomosis is formed. (5) Within 

 the pelvis the sciatic gives twigs to the adjacent muscles, 

 nerves, and pelvic viscera. 



The Great Sacrosciatic Ligament. Figs. 126, 114. 



This is a very strong band of fibres extending from the 

 posterior, superior, and inferior iliac spines, and from the 

 side and posterior surface of the sacrum and coccyx to the 

 inner margin of the tuberosity of the ischium, along which 

 it is prolonged as a long curved band (the falciform pro- 

 cess) for an inch and a half. 



A part of the fibres of the great sacrosciatic ligament 

 pass into the tendon of the long head of the biceps (flexor 

 biceps femoris). 



This muscle then may be said to take an origin from the 

 surface from which this ligament rises. 



The great sacrosciatic ligament converts the small sacro- 

 sciatic notch into a foramen (assisted by the small ligament 

 of the same name). 



From the posterior surface of the ligament the gluteus 

 maximus arises ; from the anterior surface some fibres of 

 the pyriformis. 



To the outer margin the deeper lamina of the fascia lata 

 is attached ; at its inner border it becomes continuous with 

 the obturator fascia. 



