852 THE NERVOUS SYSTEM. 



inverse proportion to that of the ilio-hypogastic. Occasionally it is very small, 

 and ends by joining the ilio-hypogastric ; in such cases a branch from the ilio- 

 hypogastric takes the place of the ilio-inguinal, or the latter nerve may be alto- 

 gether absent. 



The Genito-crural Nerve arises from the first and second lumbar nerves. It 

 passes obliquely through the substance of the Psoas, and emerges from its inner 

 border at a level corresponding to the intervertebral substance between the third 

 and fourth lumbar vertebrae. It descends on its surface for a variable distance, 

 and divides into a genital and crural branch. 



FIG. 504. The lumbar plexus and its branches. 



The genital branch passes outward on the Psoas magnus, near the external 

 iliac artery, to which it gives a twig. It then pierces the fascia transversalis or 

 passes through the internal abdominal ring, descends along the back part of the 

 spermatic cord to the scrotum in the male, and supplies the Cremaster muscle. 

 In the female it accompanies the round ligament. 



The crural branch descends on the external iliac artery, sending a few fila- 

 ments round it, and, passing beneath Poupart's ligament into the thigh, enters the 

 sheath of the femoral vessels lying superficial and a little external to the femoral 

 artery, to which it also supplies a few filaments. It pierces the anterior layer of 

 the sheath of the vessels, and, becoming superficial by passing through the fascia 

 lata, it supplies the skin of the anterior aspect of the thigh as far as midway 

 between the pelvis and knee. On the front of the thigh it communicates with 

 the outer branch of the middle cutaneous nerve, derived from the anterior crural. 



