THE ANTERIOR CRURAL NERVE 159 



leaves the plexus in conjunction with the anterior crural nerve, or it 

 may be a branch of the latter nerve. The largest branch accompanies 

 the iliaco-muscular artery and runs across the iliacus muscle. They 

 supply the psoas and iliacus muscles. 



THE ANTERIOR CRURAL NERVE 



The anterior crural nerve is the largest branch given off by the 

 anterior division of the plexus^ and of the branches of the whole plexus 

 it is second in size only to the great sciatic nerve. Its fibres are derived 

 from the contributions to the plexus which come from the inferior 

 primary divisions of the fourth and fifth lumbar nerves, and in part 

 also from the slender contribution which is furnished by the third 

 lumbar. 



At first the nerve is found above the psoas parvus muscle, across the 

 superior surface of which it runs. It then descends between this muscle 

 and the psoas magnus, where in a dissection of the sublumbar region it 

 may readily be found. The nerve next runs for a short distance down- 

 wards and outwards, following the course of the external iliac artery, and 

 crosses the conical muscular mass which forms the common posterior 

 extremity of the psoas magnus and iliacus muscles, where it is covered 

 by the sartorius. Whilst under cover of this muscle it gives off the 

 internal saphena nerve, and it then terminates by splitting up into a 

 number of branches, which dip in between the vastus internus and rectus 

 femoris muscles to supply these and the remaining two divisions of the 

 quadriceps extensor cruris. 



The internal saphena nerve is a branch of the anterior crural, trom 

 which it is detached a little above the brim of the pelvis. Near Poupart's 

 ligament it is found sHghtly in front of the femoral artery, to which 

 vessel it distributes branches. Running at first parallel to the sartorius 

 muscle, to which it also furnishes branches, it splits up into two cutaneous 



