NERVES. 



Genito-crural. Arising by two roots which unite in the 

 Psoas, the nerve then pierces and descends on the front of the 

 Psoas, rims through the psoas fascia, alone; the outer side of the 

 iliac vessels, and divides above Pou part's ligament into two 

 branches, viz.: The genital branch runs across the external 

 iliac vessels and through the inguinal canal to the skin of the 

 scrotum (or labium majus) and adjacent thigh; branches go 

 to the external iliac artery, Cremaster, and (sympathetic) sper- 

 matic plexus. The crural branch descends on the outer side of 

 the femoral artery to the thigh. [643] 



External Cutaneous. This runs under the Psoas, then 

 across the Iliacus (under the iliac fascia) to the anterior supe- 

 rior spine and then under the end of Poupart's ligament to the 

 thigh. [643] 



Obturator. This arises by three roots which, in front of the 

 anterior crural, unite in the Psoas and emerge at its inner bor- 

 der. The nerve then descends behind the common iliac and 

 along the outer side of the internal iliac vessels, runs forward 

 below the pelvic brim with the obturator artery, and entering 

 the obturator canal divides into two branches, superficial and 

 deep; these pass to the thigh. [643] 



Anterior Crural. This arises by three roots which unite in 

 the Psoas and emerge at its outer border. The nerve descends 

 between the Psoas and Iliacus, sending a branch to the latter, 

 and runs under Poupart's ligament, external to the femoral 

 sheath, to the thigh. [645] 



SACRAL (SCIATIC) PLEXUS. 



This lies at the back of the pelvis, between the Pyriformis 

 and parietal fascia; it is formed by part of the fourth lumbar, 

 the fifth lumbar, and the first three sacral nerves. The nerves 

 converge into a triangular band whose apex runs through 

 the great sacro-sciatic foramen below the Pyriformis, and then 

 into the buttock as the great sciatic nerve. The lumbar and 

 first two sacral nerves each divide into anterior and posterior 



[201] 



