604 THE LUMBAR Is^ERVES. 



Varieties. — Occasional c7itancovs urrre. — In some instances tlie communicat- 

 ing branch described is larger than usual, and descends along the posterior border 

 of the sartorius to the inner side of the knee, where it perforates the fascia, com- 

 municates with the internal saphenous nerve, and extends down the inner side of 

 the limb, supplying the skin as low as the middle of the leg. 



"Wlien this cutaneous branch of the obturator nerve is present, tile internal 

 cutaneous branch of the anterior cnaral nerve is small, the size of the two nerves 

 bearing an inverse proportion to each other. 



Acccs.w?-!/ ohfnrafor /irrir. — The accessory obturator nerve, a small and incon- 

 stant nerve, arising from the obturator nerve near its upper end, or separately 

 from the same nerves of the plexus, descends along the inner border of the psoas 

 muscle, over the pubic bone, and, passing behind the pectineus muscle, ends by 

 dividing into several branches. Of these one joins the anterior branch of the 

 obturator nerve ; another penetrates the pectineus on the under surface ; whilst 

 a third enters the hip- joint ■with the articiilar artery. 



This nerve is sometimes smaller than usual, and ends in filaments which perfo- 

 rate the capsule of the hip-joint. When it is altogether wanting, the hip-joint 

 receives branches from the obtui-ator nerve. 



SusiMAEY. — The obturator nerve and accessory obturator give 

 branches to the hip and knee joints, also to the adductor muscles of the 

 thigh, and, in some cases, to the pectineus. Occasionally a cutaneous 

 branch descends to the inner side of the thigh, and to the inner and 

 upper part of the leg. 



Anterior crural nerve. 



This nerve is the largest branch of the lumbar plexus, and is de- 

 rived principally from the third and fourth lumbar nerves, but in 

 part also from the second. Emerging from the outer border of the 

 psoas muscle, near its lovrer part, it descends into the thigh in the 

 groove between that muscle and the iliacus, and, therefore, to the 

 outside of the femoral blood-vessels. It now becomes flattened out 

 and divides into two parts, one of which is cutaneous, while the other 

 is distributed to muscles. 



Bra]s^ches of the teuxk. — The branches given from the anterior 

 crural nerve within the abdomen are few and of small size. 



(«) The Uiacuf: receives thi'ee or four small branches, which are directed out- 

 wards from the nerve to the fore part of the muscle. 



(Jj) The ncrrc oftlic femoral arfc7-ij is a small branch which divides into numerous 

 filaments upon the upper part of that vessel. It sometimes arises lower do^^^x 

 than usual in the thigh. It may, on the other hand, be found to take origin 

 above the ordinary position ; and in this case it proceeds from the middle cutaneous 

 nerve, when that branch springs from or near the lumbar plexus. In either case 

 its ultimate distribution is the same as that already described. 



Terminal branches. — From the principal or terminal divisions of 

 the nerve the remaining branches take their rise as follows. 



From the si/per/icial division cutaneous branches are given to the fore 

 part of the thigh, and to the inner side of the leg. They are the middle 

 and internal cutaneous nerves, and the internal saphenous nerve. One 

 of the muscles, the sartorius, receives its nerves from this group. 



The (Jeep hranclics supply the muscles on the fore part of the thigh, 

 and also the pectineus muscle. The branch to the pectineus, however, 

 sometimes arises from the superficial part of the trunk. 



A. Muscular branches. — The branch to the 2^('cti?ieus muscle crosses inwards 

 behind the femoral vessels, and enters the muscle on the anterior aspect. 



