ABDOMINAL CAVITY 407 



along the medial side of the psoas major, 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 sometimes supplies a 

 twig to the pectineus muscle. 



Truncus Lumbosacralis (O.T. Lumbo-sacral Cord). The 

 lumbo-sacral trunk is formed by the union of the anterior 

 ramus of the fifth lumbar nerve with the descending branch 

 of the fourth lumbar nerve. It passes downwards over the 

 base of the sacrum, behind the common iliac artery, into the 

 pelvis minor, where it joins the sacral plexus. 



Last Thoracic Nerve. The anterior ramus of the last 

 thoracic 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 vertebral column 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 trans- 

 versus 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. 217). 



Arterise Lumbales. The lumbar arteries have been 

 traced to the medial border of the psoas major. Thence 

 they pass backwards, medial to the psoas major, to the intervals 

 between the transverse processes of the vertebrae, where each 

 gives off a dorsal branch. 



Each dorsal branch runs backwards, between the adjacent 

 transverse processes, and after giving a spinal branch which 

 enters the vertebral canal through the intervertebral foramen, 

 it ends in the muscles and integument of the back. 



After giving off their dorsal branches, the trunks of the 

 arteries, with the exception of the last, proceed laterally behind 

 the psoas and the quadratus lumborum, and are then directed 

 forwards between the internal oblique and transversus muscles, 

 where they anastomose, superiorly, with the intercostal arteries, 

 inferiorly, with the deep circumflex iliac and ilio -lumbar 

 arteries, and anteriorly ', with the branches of the superior and 

 inferior epigastric arteries. The last lumbar artery, as a rule, 

 passes in front of the quadratus lumborum. 



Venae Lumbales. The lumbar veins accompany the 

 corresponding arteries. The first, and sometimes the second, 

 ii 26 c 



