NERYES OF LOWER EXTREMITIES. 653 



and divides into an anterior and a posterior branch, separated by the Adductor 

 Brevis muscle. 



The anterior branch (Fig. 356) passes down in front of the Adductor Brevis, 

 being covered by the Pectineus and Adductor Longus; and at the lower border 

 of the latter muscle, communicates with the internal cutaneous and internal 

 saphenous nerves, forming a kind of plexus. It then descends upon the femo- 

 ral artery, upon which it is finally distributed. 



This nerve, near the obturator foramen, gives off an articular branch to the 

 hip-joint. Behind the Pectineus, it distributes muscular branches to the Ad- 

 ductor Longus and Gracilis, and occasionally to the Adductor Brevis and Pec- 

 tineus, and receives a communicating branch from the accessory obturator 

 nerve. 



Occasionally this communicating branch is continued down, as a cutaneous 

 branch, to the thigh and leg. This occasional cutaneous branch emerges from 

 the lower border of the Adductor Longus, descends along the posterior margin, 

 of the Sartorius to the inner side of the knee, where it pierces the deep fascia, 

 communicates with the long saphenous nerve, and is distributed to the integu- 

 ment of the inner side of the leg, as low down as its middle. When this 

 branch is small, its place is supplied by the internal cutaneous nerve. 



The posterior branch of the obturator nerve pierces the Obturator Externus, 

 and passes behind the Adductor Brevis to the front of the Adductor Magnus, 

 where it divides into numerous muscular branches, which supply the Obturator 

 Externus, the Adductor Magnus, and, occasionally, the Adductor Brevis. 



The articular branch for the knee-joint perforates the lower part of the Adductor 

 Magnus, and enters the popliteal space ; it then descends upon the popliteal ar- 

 tery, as far as the back part of the knee-joint, where it perforates the posterior 

 ligament, and is distributed to the synovial membrane. It gives filaments to 

 the artery in its course. 



The Accessory Obturator Nerve (Fig. 354) is of small size, and arises either 

 from the obturator nerve near its origin, or by separate filaments from the 

 third and fourth lumbar nerves. It descends along the inner border of the 

 Psoas muscle, crosses the body of the pubes, aud passes beneath the Pectineus 

 muscle, where it divides into numerous branches. One of these supplies the 

 Pectineus, penetrating its under surface ; another is distributed to the hip-joint ; 

 while a third communicates with the anterior branch of the obturator nerve. 

 This branch, when of large size, is prolonged (as already mentioned), as a 

 cutaneous branch, to the leg. The accessory obturator nerve is not constantly 

 found : when absent, the hip-joint receives branches from the obturator nerve. 

 Occasionally it is very small, and becomes lost in the capsule of the hip-joint. 



The Anterior Crural Nerve (Figs. 354, 356) is the largest branch of the lumbar 

 plexus. It supplies muscular branches to the Iliacus, Pectineus, and all the 

 muscles on the front of the thigh, excepting the Tensor Vagina Femoris ; cuta- 

 neous filaments to the front and inner side of the thigh, and to the leg and foot ; 

 and articular branches to the knee. It arises from the third and fourth lumbar 

 nerves, receiving also a fasciculus from the second. It descends through the 

 fibres of the Psoas muscle, emerging from it at the lower part of its outer bor- 

 der ; and passes down between it and the Iliacus, and beneath Poupart's liga- 

 ment, into the thigh, where it becomes somewhat flattened, and divides into an 

 anterior or cutaneous, and a posterior or muscular part. Beneath Poupart's 

 ligament, it is separated from the femoral artery by the Psoas muscle, and lies 

 beneath the iliac fascia. 



Within the pelvis, the anterior crural nerve gives off from its outer side some 

 small branches to the Iliacus, and a branch to the femoral artery, which is dis- 

 tributed upon the upper part of that vessel. The origin of this branch varies; 

 it occasionally arises higher than usual, or it may arise lower down in the 

 thigh. 



