786 THE NERVOUS SYSTEM. 



supply the Adductor magnus, and the Adductor brevis when the latter does not 

 receive a branch from the anterior division of the nerve. One of the branches 

 gives off a filament to the knee-joint. 



The articular branch for the knee-joint is sometimes absent ; it perforates the 

 lower part of the Adductor magnus, and enters the popliteal space ; it then 

 descends upon the popliteal artery, 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. 417) is not constantly present. It is of 

 small size, and arises by separate filaments from the third and fourth lumbar nerves. 

 It descends along the inner border of the Psoas muscle, crosses the ascending ramus 

 of the os pubis, and passes under the outer border of the Pectineus muscle, where 

 it divides into numerous branches. One of these supplies the Pectineus, pene- 

 trating its under surface ; another is distributed to the hip-joint ; while a third 

 communicates with the anterior branch of the obturator nerve. When this nerve 

 is absent the hip-joint receives two branches from the obturator nerve. Occasion- 

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



The Anterior Crural Nerve (Figs. 417, 419) 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 fascise femoris ; cutaneous 

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

 articular branches to the hip and knee. It arises from the second, third, and foui'th 

 lumbar nerves. It descends through the fibres of the Psoas muscle, emerging from 

 it at the lower part of its outer border, and passes down between it and the Iliacus, 

 and beneath Poupart's ligament, into the thigh, where it becomes somewhat flat- 

 tened, and divides into an anterior and a posterior part. Under Poupart's liga- 

 ment it is separated from the femoral artery by a portion of the Psoas muscle, and 

 lies beneath the iliac fascia. 



Within the abdomen 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 distrib- 

 uted 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. 



External to the pelvis the following branches are given off : 



From the Anterior Division. From the Posterior Division. 

 Middle cutaneous. Long saphenous. 



Internal cutaneous. Muscular. 



Muscular. Articular. 



The middle cutaneous nerve (Fig. 418) pierces the fascia lata (generally the 

 Sartorius also) about three inches below Poupart's ligament, and divides into two 

 branches, which descend in immediate proximity along the fore part of the thigh, 

 to supply the integument as low as the front of the knee, where it communicates 

 with the internal cutaneous and the patellar branch of the internal saphenous 

 nerve, to form the patellar plexus. In the upper part of the thigh the outer 

 division of the middle cutaneous communicates with the crural branch of the 

 genito-crural nerve. 



The internal cutaneous nerve passes obliquely across the upper part of the 

 sheath of the femoral artery, and divides in front or at the inner side of that vessel 

 into two branches, anterior and posterior or internal. 



The anterior branch runs downward on the Sartorius, perforates the fascia lata 

 at the lower third of the thigh, and divides into two branches, one of which 

 supplies the integument as low down as the inner side of the knee ; the other 

 crosses to the outer side of the patella, communicating in its course with the 

 nervus cutaneus patellae, a branch of the internal saphenous nerve. 



The posterior or internal branch descends along the inner border of the 

 Sartorius muscle to the knee, where it pierces the fascia lata, communicates with 



