598 THE DORSAL NERVES, 



The jwsterio)' hranchcs bend back-^-ards over the latissimus dorsi muscle, 

 (1)) The anterior cutaneous nerves of the abdomen become subcutaneous 

 near the linea alba, accompanying the small perforating arteries. Tlieir number 

 and position are very uncertain. They are directed outwards towards the lateral 

 cutaneous nerves. A second set is described by Cruveilhier as existing at the 

 outer edge of the rectus muscle. 



LAST DOKSAL NERVE. 



The anterior primary division of this nerve is below the last rib, and 

 is contained altogether in the abdominal wall. The nerve has the 

 general course and distribution of the others between the internal 

 oblique and transversalis, but, before taking its place between those 

 muscles, it passes in front of the upper part of the quadratus lumborum, 

 and pierces the posterior aponeurosis of the transverse muscle. This 

 nerve is connected by offsets with the nerve above, and occasionally 

 with the ilio-hypogastric branch of the lumbar plexus. Near the spine 

 it sometimes communicates with the first lumbar nerve by means of a 

 small cord in the substance of the quadratus lumborum. 



The lateral cntaneotis branch of the last dorsal nerve, passing 

 through both oblique muscles, is directed downwards over the iliac 

 crest to the integument, covering the fore part of the gluteal region 

 and the upper and outer part of the thigh, some filaments reaching as 

 far as the great trochanter of the femur. 



LUMBAR NESVES, 



The anterior divisions of the lumbar nerves increase in size from the 

 first to the fifth ; and all, except the fifth, which passes down to join 

 the sacral nerves, are connected together by communicating loops, so as 

 to form the lumbar plexus. On leaving the intervertebral foramina 

 these nerves are connected by filaments with the sympathetic nerve, 

 these filaments being longer than those connected with other sjiinal 

 nerves, in consequence of the position of the lumbar sympathetic 

 ganglia on the fore part of the bodies of the vertebra3. In the same 

 situation are furnished small twigs to the psoas and quadratus lum- 

 borum muscles. 



LUMBAR PLEXUS. 



The lumbar plexus is formed by the communications between the 

 anterior primary divisions of the four upper lumbar nerves. It is 

 placed in the substance of the psoas muscle, in front of the transverse 

 processes of the corresponding vertebrge. Above, the plexus is narrow, 

 and is sometimes connected with the last dorsal nerve by a small offset 

 from that nerve, named dorsi-luml)ar ; below it is wider, and is joined 

 to the sacral plexus by means of a branch given by the fourth lumbar 

 nerve to the fifth. 



The arrangement of the jilexus may be thus stated. The first nerve 

 gives off the ilio-hypogastric and ilio-inguinal nerves, nnd sends down- 

 wards a communicating branch to the second nerve. The second 

 furnishes the greater part of the genito-crural and external cutaneous 

 nerves, and gives a connecting branch to the third, from which some of 

 the fibres of the anterior crural and obturator nerves are derived. 

 From the third nerve, besides the descending branch to the fourth. 



