THE NERVES. 413 



662. III. The lumbar, abdominal nerves, Nervi lumbales, 

 (eight pairs.) 



The first passes out between the twelfth dorsal and first lumbar 

 vertebra, the fifth between the fifth abdominal and the sacrum. 

 Their roots lie closer together, belong to the cauda equina, and 

 pass tolerably far downwards in the canal, spinalis ; they are not 

 united, like the earlier spinal nerves, by means of interposed fila- 

 ments. The ganglia of the lower are situated in the canalis spi- 

 nalis. The trunk divides, soon after its exit from the interverte- 

 bral foramen, into an anterior and posterior branch. 



The anterior branches increase at the origin from the first to 

 the fifth, unite by means of two or several filaments with n. sym~ 

 pathicuS) pass through m. psoas major, and associate in loops be- 

 fore the transverse processes of the abdominal vertebrae, the four 

 superior of which form plex. lumbalis, while the fifth belongs to 

 the plex. sacralis. 



2. The posterior branches decrease in size from the first to the 

 fifth, are soon reflected backwards between the transverse pro- 

 cesses and their muscles, and divide into : 



a. Internal branches. They pass in the groove on the basis of 

 the transverse process to m. muUifidus and inter spinales. 

 The fifth branch unites with the first n. sacralis. 



b. External branches. They are larger, go to mm. intertrans- 

 versarii and sacro-lumbalis. The three first distribute nn. 

 cutanei superior es \lumbo-glut<zal} to the glutseal region. 



663. Plexus lumbalis. 



The lumbar plexus is formed by the loops of the second, third, 

 fourth, and a small branch of the first abdominal nerve, and is 

 situated on the sides of the bodies of the lumbar vertebrae between 

 the transverse processes and the fasciculi of psoas major. Three 

 secondary and three principal branches pass off from it, the for- 

 mer of which belong to the first and second lumbar nerves as 

 nn. abdominales, and pass between m. psoas and iliacus on one 

 side and the peritoneum on the other, to the crural arch ; the 

 latter supply the inferior extremity. 



664. a. The secondary branches, abdominal branches. 



1. JV. ileo-hypogastricus arises from the first lumbar nerve, 

 perforates the psoas, passes outwards before m. quadrat, lumbar. 

 downwards towards the crista ilei, penetrates m. transvers. abdom., 

 passes, between m. transversus and obliquus internus, along the 



