1050 THE NERVE SYSTEM 



male (nn. scrotales anteriores) and to the skin covering the mons veneris and 

 labium majus in the female (nn. labiales anteriores). The size of this nerve is 

 in inverse proportion to that of the iliohypogastric. Occasionally it is very small, 

 and ends by joining the iliohypogastric; in such cases a branch from the iliohypo- 

 gastric takes the place of the ilioinguinal, or the ilioinguinal nerve may be alto- 

 gether absent. 



The genitofemoral or genitocmral nerve (n. yenitofemoralis) (Figs. 768 and 769) 

 arises from the first and second lumbar nerves. It passes obliquely through 

 the substance of the Psoas magnus muscle, and emerges from its inner border at 

 a level corresponding to the intervertebral substance between the third and fourth 

 lumbar vertebra?; it then descends on the surface of the Psoas muscle, under cover 

 of the peritoneum, and divides into a genital and a femoral branch. 



The genital branch or external spermatic nerve (n. spermaticus externus) passes 

 outward on the Psoas magnus, and pierces the fascia transversalis, or passes 

 through the internal abdominal ring; in the male it then descends along the back 

 part of the spermatic cord to the scrotum, and supplies the Cremaster muscle. 

 In the female it accompanies the round ligament, and is lost upon it. 



The femoral branch or lumboinguinal nerve (n. lumboinguinalis) (Fig. 770) 

 descends on the external iliac artery, sending a few filaments around it, and, 

 passing beneath Poupart's ligament to the thigh, enters the sheath of the femoral 

 vessels, lying superficial and a little external to the femoral artery. 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 com- 

 municates with the outer branch of the middle cutaneous nerves, derived from the 

 femoral nerve. A few filaments from this nerve may be traced on to the femoral 

 artery; they are devived from the nerve as it passes beneath Poupart's ligament. 



The External or Lateral Cutaneous Nerve (n. cutaneus femoris lateralis) (Figs. 

 769 and 770) arises from the second and third lumbar nerves. It emerges from 

 the lateral border of the Psoas magnus muscle, about its middle, and crosses the 

 Iliacus muscle obliquely, toward the anterior superior spine of the ilium. It then 

 passes under Poupart's ligament and over the Sartorius muscle into the thigh, 

 where it divides into two branches, anterior and posterior. 



The anterior branch descends in an aponeurotic canal formed in the fascia lata, 

 becomes superficial about four inches below Poupart's ligament, and divides 

 into branches which are distributed to the integument along the anterior and outer 

 part of the thigh, as far down as the knee. The terminal filaments of this nerve 

 frequently communicate with the middle and internal cutaneous and with the 

 patellar branch of the long saphenous nerve, forming with them the patellar plexus. 



The posterior branch pierces the fascia lata, and subdivides into branches which 

 pass backward across the outer and posterior surface of the thigh, supplying the 

 integument from the level of the great trochanter to the middle of the thigh. 



The Obturator Nerve (n. obturatorius) (Figs. 769 and 771) supplies the Obturator 

 externus and Adductor muscles of the thigh, the articulations of the hip and knee, 

 and occasionally the integument of the thigh and leg. It arises from the second, 

 the third, and the fourth lumbar nerves. Of these, the branch from the third 

 is the largest, while that from the second is often very small. It descends through 

 the inner fibres of the Psoas magnus muscle, and emerges from its inner border 

 near the brim of the pelvis; it then passes behind the external iliac vessels, which 

 separate it from the ureter, and runs along the lateral wall of the pelvis, above the 

 obturator vessels, to the upper part of the obturator foramen. Here it enters 

 the thigh, and divides into an anterior and a posterior branch, which are separated 

 by some of the fibres of the Obturator externus muscle, and lower down by the 

 Adductor brevis muscle. 



