358 The Lumbar Nerves 



The anterior crural nerve emerges frcm the cuter side of the 

 psoas, beneath the iliac fascia, and lies between the psoas and iliacus, 

 both of which it supplies. Having passed beneath Poupart's ligament, 

 and beneath the outer part of the crural sheath, it divides, in the upper 

 part of Scarpa's triangle, into cutaneous and muscular branches. 



The first-named branches are : the middle cutaneous, which pierce 

 the sartorius to end in the front of the thigh ; the internal cutaneous, 

 which cross the front of the superficial femoral artery for the inner side of 

 the thigh and even the upper part of the leg. Filaments of the internal 

 cutaneous nerve, beneath the fascia latajoin the middle cutaneous and 

 the internal saphenous nerve in the formation of the patellar plexus. 



The largest of the cutaneous branches of the anterior crural nerve 

 is the internal saphenous, which crosses the artery obliquely from the 

 outer side and lies in front of it in Hunter's canal, but, though in the 

 canal, it is not within the proper sheath of the vessels. It leaves the 

 canal with the superficial part of the anastomotica magna, and, cours- 

 ing behind the sartorius to the knee, it pierces the fascia lata to lie by 

 the internal saphenous vein ; it ends at the ball of the great toe. It 

 gives branches to the obturator and patellar plexus and to the inner 

 side of the leg and foot. 



Muscular branches. In addition to those given off in the false 

 pelvis to the psoas and iliacus, the anterior crural sends a branch 

 beneath the crural sheath to the pectineus ; to the rectus, which gives a 

 twig to the hip-joint ; to the vastus externus, which reaches the interior 

 of the knee-joint ; to the crureus and sub-crureus (which, also, may 

 supply the knee-joint) ; and a large branch to the vastus internus, 

 which journeys with, but to the outer side of, the long saphenous nerve. 

 The sartorius may receive branches from the anterior crural as well 

 as from the middle cutaneous. 



Neuralgia of the anterior crural may be due to central disease of 

 the cord, as in locomotor ataxy ; to pressure upon the posterior roots 

 as they leave the spinal canal, as in the case of spinal tumour, 

 meningitis, or lumbar caries ; to inflammation of, or abscess in, the 

 psoas ; to the pressure of enlarged lumbar glands, or of iliac aneurysm ; 

 to inflammatory thickening of the fibrous elements of the nerve, or to 

 reflected irritation, as in the case of hip-joint disease. 



The strange way in which the ultimate branches of a nerve may be 

 distressed in the case of central pressure was well exemplified in a 

 child with spinal caries, whose chief symptom seemed to be sym- 

 metrical darting pains at the ball of each great toe at the endings of 

 the internal saphenous nerves. 



The obturator nerve descends along the inner border of the psoas, 

 and through the fork of the external and internal iliac arteries, and out 

 by the upper part of the thyroid foramen, above the obturator artery. 

 It divides into a superficial and a deep branch. 



The superficial division passes down in front of the adductor brevis 



