DISSECTION OF THE ABDOMEN. 325 



2. The Anterior or great crural nerve (Plate 45). This is a large 

 nerve which derives its fibres from the 4th and 5th lumbar roots, and 

 from the loop between the 3rd and 4th. Emerging between the psoas 

 magnns and parvus, it descends at the outer side of the external iliac 

 artery, but separated from it by the tendon of the last-named muscle. 

 It rests on the iliacus and psoas muscles, and crosses their common 

 termination to end in a fasciculus of branches for the extensors of the leg. 

 In this course it is covered by the sartorius muscle. It gives off as a 

 branch the internal saphenous nerve, whose origin is about opposite the 

 ilio-pectineal eminence. 



The Aortic Plexus of the Sympathetic Nerve (Plate 45). This is the 

 backward continuation of the solar plexus. Its branches interlace around 

 the aorta behind the kidneys, and unite with the posterior mesenteric 

 plexus. It receives some of the efferent filaments of the lumbar ganglia. 



The Posterior Mesenteric Plexus is formed around the root of the 

 artery of the same name. It is united in front with the aortic plexus, 

 and receives efferent branches from the lumbar ganglia. Three sets of 

 branches pass from it: — 



1 . Branches following the divisions of the posterior mesenteric artery. 



2. Branches accompanying the spermatic artery, and forming the 

 spermatic plexus. 



3. Pelvic branches to join the pelvic plexus. 



The Sympathetic Gangliatbd Cord in the loins. This is the back- 

 ward continuation of the dorsal cord. Beginning between the psoas 

 parvus and the diaphragmatic cms, it extends backwards to the lumbo- 

 sacral articulation, where it is directly continued by the sacral division 

 of the cord. Each nerve will be found on the inner aspect of the psoas 

 pai-vus muscle of the same side, the left nerve being related inwardly to 

 the aorta; and the right for the greater part of its course to the vena 

 cava, but for a short distance in front to the aorta. Six fusiform, 

 greyish ganglia stud the cord, and from these proceed the various 

 branches of the cord. These branches are : — 



1. Communicating branches with the inferior primary divisions of the 

 lumbar spinal nerves. 



2. Branches to the aortic and posterior mesenteric plexuses. 



Iliac Fascia. This is the name given to the aponeurotic layer which 

 covers the inferior face of the psoas magnus and iliacus muscles. It is 

 densest and most adherent at the side of the pelvic inlet, and becomes 

 more cellular as it is traced forwards and backwards. It is adherent 

 inwardly to the psoas parvus tendon, and outwardly to the bony promi- 

 nence of the haunch. Poupart's ligament is adherent to its inferior face, 

 and it gives origin to the sartorius and cremaster muscles. 



The Psoas Magnus (Plates 44 and 45). This muscle is broad and 

 flattened anteriorly, and thick and pointed behind, where it rests in 



