156 TOPOGRAPHICAL ANATOMY OF THE 



N. FEMORALis. — The femoral nerve is much larger than any of the 

 foregoing, and is formed by roots from tlie fourth and fifth (possibly 

 also the sixth) lumbar nerves. The third nerve also commonly con- 

 tributes a small root. The femoral nerve lies at first between the 

 greater and lesser psoas muscles, and afterwards on the lateral surface 

 of the tendon of the psoas minor. It enters the thigh under cover of 

 the sartorius in company with the ilio-psoas muscle, and just before 

 doing so, gives origin to the fia'plienouK nerve (n. saphenus). A 

 collateral branch is furnished to the ilio-psoas muscle. The distri- 

 bution of the nerve to the quadriceps femoris muscle is examined 

 during the dissection of the thigh. 



N. SYMPATHICUS. — The gangliated cord of the sympathetic in the 

 abdomen is a continuation of a similar cord in the thorax. Passing 

 from the thoracic cavity between a crus (right or left) of the diaphragm 

 and the psoas minor muscle, the cord ranges itself along the medial 

 border of the latter, runs through the entire lumbar region, and is 

 continued into the pelvis. Irregular spindle-shaped ganglia, six in 

 number, occur at intervals along the cord, and are connected by rami 

 communicantes with the lumbar nerves. 



Filaments from the ganglia pass to the lumbar blood vessels, and 

 larger nerves proceed to the coeliaco-mesenteric and caudal mesenteric 

 ganglia and the plexuses that lie about the aorta (plexus aorticus 

 abdominalis) and within the pelvis. 



The Pelvic Cavity. 



The pelvic cavity (cavum pelvis) is bounded by the sacrum, the first 

 two coccygeal vertebrie^ and the two hip bones. Cranially it communi- 

 cates freely with the cavity of the abdomen proper by the cranial 

 'pelvic aperture or pelvic inlet, bounded by the terminal line or pelvic 

 brim. The dorsal wall of the cavity is formed by the sacrum and two 

 coccygeal vertebne. The lateral walls are only partly bony, those parts 

 of the ilia caudal to the ilio-pectineal lines alone being concerned in 

 their formation. The rest of the wall on each side is formed by the 

 extensive sheet consisting of the fused sacro-spinous and sacro- tuberous 

 ligaments. Between the ilium and the sacro-spinous ligament there is 

 a defect in the wall, the greater sciatic ' foramen, containing loose 

 connective tissue surrounding nerves and blood vessels ; and another 



' The definition of the caudal limit of the i)elvic cavity is not very precise. 

 Some writers include only one coccygeal vertebra in the boundary of the cavity ; 

 others consider that three should be included. 



^ Sciatiais [L.], iVx'«5t(c6s (ischiadicos) [Gr.], pertaining to the ischium. 



