THE LUMBAR PLEXUS. 855 



The Anterior Crural Nerve (Figs. 504, 506) is the largest branch of the lumbar 

 plexus. It supplies muscular branches to the Iliacus, Pectineus, and all the 

 muscles on the front of the thigh, excepting the Tensor vaginae femoris ; cutaneous 

 filaments to the front and inner side of the thigh and to the leg and foot ; and 

 articular branches to the hip and knee. It arises from the second, third, and 

 fourth lumbar nerves. It descends through the fibres of the Psoas muscle, 

 emerorino' from it at the lower part of its outer border, and passes down between 

 it and the Iliacus, and beneath Pouparf s ligament, into the thigh, where it becomes 

 somewhat flattened, and divides into an anterior part which passes superficial to 

 the external circumflex vessels, and a posterior part which passes beneath these 

 vessels. Under Poupart's ligament it is separated from the femoral artery by the 

 Ps 'as muscle, and lies beneath the iliac fascia. 



Within the pelvis the anterior crural nerve gives off from its outer side some 

 small branches to the Iliacus. and a branch to the femoral artery which is distrib- 

 uted upon the upper part of that vessel. The origin of this branch varies : it 

 occasionally arises higher than usual, or it may arise lower down in the thigh. 



External to the pelvis the following branches are given off: 



From the Anterior Division. From the Posterior Division. 

 Middle cutaneous. Long saphenous. 



Internal cutaneous. Muscular. 



Muscular. Articular. 



Anterior Division. The middle cutaneous nerve (Fig. 505) pierces the fascia 

 lata about three inches below Poupart's ligament, and divides into two branches, 

 which descend in immediate proximity along the fore part of the thigh, dis- 

 tributincr numerous branches to the integument as low as the front of the knee. 



O C3 



where it communicates Avith the nervus cutaneus patellce, a branch of the internal 

 saphenous nerve, helping to form the patellar plexus. Its outer branch communi- 

 cates, above, with the crural branch of the genito-crural nerve, and the inner 

 branch with the internal cutaneous nerve below. The Sartorius muscle is fre- 

 quently pierced by this nerve or by its outer branch. 



The internal cutaneous nerve passes obliquely across the upper part of the 

 sheath of the femoral artery, and divides in front or at the inner side of that vessel 

 into two branches, anterior and posterior or internal. 



The anterior branch runs downward on the Sartorius, perforates the fascia lata 

 at the lower third of the thigh, and divides into two branches, one of which 

 supplies the integument as low down as the inner side of the knee ; the other 

 crosses to the outer side of the patella, communicating in its course with the 

 nervus cutaneus patellae, a branch of the internal saphenous nerve. 



The posterior or internal branch descends along the inner border of the 

 Sartorius muscle to the knee, where it pierces the fascia lata, communicates with 

 the long saphenous nerve, and gives off several cutaneous branches. The nerve 

 then passes clown the inner side of the leg, to the integument of which it is 

 distributed. This nerve, beneath the fascia lata, at the lower border of the 

 Adductor longus, joins in a plexiform network by uniting with branches of the 

 long saphenous and obturator nerves (Fig. 506). When the communicating branch 

 from the obturator nerve is large and continued to the integument of the leg, the 

 inner branch of the internal cutaneous is small and terminates at the plexus, 

 occasionally giving off a few cutaneous filaments. 



The internal cutaneous nerve, before dividing, gives off a few filaments, which 

 pierce the fascia lata. to supply the integument of the inner side of the thigh, 

 accompanying the long saphenous vein. One of these filaments passes through 

 the saphenous opening ; a second becomes subcutaneous about the middle of the 

 thigh ; and a third pierces the fascia at its lower third. 



The muscular branches supply the Pectineus and Sartorius. Those to the 

 Pectineus, often united with the internal cutaneous nerve at their origin, are 



