554 ABDOMEN 



its middle, and descends obliquely across the iliacus muscle, 

 behind the fascia iliaca, to the anterior superior spine of the 

 ilium. At this point it leaves the abdomen by passing behind 

 the inguinal ligament. It supplies the skin upon the lateral 

 and anterior aspect of the thigh. 



The nervus femoralis (O.T. anterior crural nerve] is the 

 largest branch of the plexus. It runs downwards in the 

 interval between the psoas and iliacus, and passes out of the 

 abdomen behind the inguinal ligament. It gives a branch to 

 the iliacus muscle. 



The n. obturatorius (obturator nerve] emerges from the 

 medial border of the psoas, where this muscle reaches the 

 brim of the small pelvis, and extends forwards upon the inner 

 surface of the wall of the small pelvis, a short way below the 

 ilio-pectineal line of the innominate bone. At the upper 

 part of the obturator foramen it joins the artery of the 

 same name, and, escaping from the pelvis, enters the thigh. 



A small nerve, the accessory obturator^ is occasionally to be 

 found. It may spring either directly from the obturator or 

 from the third and fourth lumbar nerves. It proceeds down- 

 wards along the medial side of the psoas, and it enters the 

 thigh by passing over the pubic bone under cover of the 

 pectineus. In the thigh it gives branches to the hip-joint, and 

 unites with the obturator nerve. It occasionally supplies a 

 twig to the pectineus muscle. 



Truncus Lumbosacralis (Lumbo-sacral Cord). This large 

 nerve trunk is formed by the union of the anterior primary 

 division of the fifth lumbar nerve with the descending branch 

 of the fourth lumbar nerve. It passes downwards over the 

 base of the sacrum into the pelvis, and joins the sacral plexus. 



Last Thoracic Nerve. The anterior primary division of this 

 nerve will be found running laterally in front of the quadratus 

 lumborum, and under cover of the fascia spread over that 

 muscle, along the lower border of the last rib. Near the 

 spine it sends a small offset downwards to the first lumbar 

 nerve, and at the lateral border of the quadratus lumborum it 

 pierces the aponeurosis of the transversalis abdominis, and 

 then passes forwards in the abdominal wall between that 

 muscle and the internal oblique. Its course and distribution 

 in the wall of the abdomen have already been described 



(P- 394). 



Arterise Lumbales (Lumbar Arteries). These have been 



