722 THE NEKVOUS SYSTEM. 



N. Genitofemoralis. The genito-femoral nerve (O.T. genito-crural) usually 

 arises by two independent roots from the front of the first and second lumbar 

 nerves, which unite in the substance of the psoas major to form a slender trunk. 

 It appears on the posterior abdominal wall, lying on the psoas major, medial to 

 the psoas- minor, and, piercing the psoas fascia, it extends downwards on the lateral 

 aspect of the common and external iliac vessels and behind the ureter, to the 

 inguinal ligament (Fig. 625, p. 721). At a variable point above that ligament it 

 divides into two branches. 1. The external spermatic branch is a small nerve. 

 It crosses the terminations of the external iliac vessels, and, along with the ductus 

 deferens and testicular and external spermatic vessels, enters the inguinal canal 

 through the abdominal inguinal ring. It terminates by supplying small branches 

 to the skin of the scrotum and adjacent part of the thigh. In the female it 

 accompanies the round ligament to the labium majus. This nerve gives off in its 

 course the following small branches : (1) to the external iliac artery ; (2) to 

 the cremaster muscle; (3) to communicate with the spermatic plexus of the 

 sympathetic. 2. The lumbo- inguinal branch continues the course of the parent 

 nerve into the thigh, lying on the lateral aspect of the femoral artery. It becomes 

 cutaneous by passing through the fossa ovalis or through the iliac portion of the 

 fascia lata, and supplies an area of skin over the femoral triangle, lateral to 

 that supplied by the ilio-inguinal nerve (Fig. 623, p. 715). It communicates 

 in the thigh with the intermediate cutaneous branch of the femoral nerve. 

 Before piercing the deep fascia it gives a minute branch to the femoral artery. 



N. Cutaneus Femoris Lateralis. The lateral cutaneous nerve of the thigh 

 is distributed only to the skin (Fig. 625). It arises from the back of the lumbar 

 plexus, and usually from the second and third lumbar nerves. Emerging from the 

 lateral border of the psoas major muscle, the nerve crosses the iliacus muscle, beneath 

 the fascia iliaca, to reach the anterior superior iliac spine. It enters the thigh beneath 

 the lateral end of the inguinal ligament, and either over, under, or through the 

 origin of the sartorius muscle. It extends distally along the front of the thigh for 

 a few inches, lying at first beneath the fascia lata, and afterwards in a tubular 

 investment of the fascia. It gives off small branches in this part of its course, and 

 finally, piercing the fascia about four inches distal to the anterior superior iliac 

 spine, it separates into anterior and posterior terminal branches. The anterior branch 

 is the larger, and is distributed on the lateral aspect of the front of the thigh almost 

 to the knee. The smaller posterior branch supplies the skin of the lateral side of 

 the buttock, distal to the greater trochanter, and the skin of the proximal two- 

 thirds of the lateral aspect of the thigh (Fig. 625, p. 721). 



OBTURATORIUS. 



The obturator nerve supplies the muscles and skin on the medial side of 

 the thigh. It arises in the substance of the psoas major muscle by three roots 

 placed in front of those of the femoral nerve, and derived from the second, third, 

 and fourth lumbar nerves (Fig. 624, p. 718). Sometimes the root from the second 

 nerve is absent. Passing vertically downwards, the nerve emerges from the psoas 

 major at its medial border, behind the common iliac, and on the lateral side 

 of the hypogastric vessels. It passes forwards below the pelvic brim in company 

 with the obturator artery to the obturator groove of the obturator foramen, through 

 which it reaches the thigh. While in the obturator groove it separates into its 

 two main branches, named anterior and posterior (Fig. 626, p. 723). 



The anterior (O.T. superficial) branch enters the thigh in front of the obturator 

 externus and adductor brevis muscles, and behind the pectineus and adductor 

 longus. In the middle third of the thigh it is found coursing along the medial 

 border of the adductor longus, anterior to the gracilis ; and it finally divides into 

 two slender terminal filaments, of which one enters the adductor canal and ends on 

 the femoral artery, while the other supplies the skin for a variable distance on the 

 medial side of the thigh and joins in the obturator plexus. 



The branches of the anterior part of the nerve are : 



