105 2 THE NERVE SYSTEM 



The anterior branch (ramus anterior} (Fig. 771) passes down in front of the 

 Adductor brevis, being covered by the Pectineus and Adductor longus; at the 

 lower border of the latter muscle, it communicates with the internal cutaneous and 

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

 femoral artery, upon which it is finally distributed. The nerve, near the obturator 

 foramen, gives off an articular branch to the hip-joint. Behind the Pectineus it 

 distributes muscular branches to the Adductor longus and Gracilis, and usually 

 to the Adductor brevis, and in rare instances to the Pectineus, and receives a 

 communicating branch from the accessory obturator nerve when that nerve is 

 present. 



Occasionally the communicating branch to the internal cutaneous and internal 

 saphenous nerves is continued down, as a cutaneous branch (ramus cutaneus), 

 to the thigh and leg. When this is so, it emerges from beneath 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 internal or long saphenous nerve, and is distributed to the integument of the 

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

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



The posterior branch (ramus posterior) pierces the anterior part of the Obturator 

 externus, sending branches to supply this muscle, and passes behind the Adductor 

 brevis on the front of the Adductor magnus, where it divides into numerous 

 muscular branches, which supply the Adductor magnus, and the Adductor brevis 

 when the latter does not receive a branch from the anterior division of the nerve. 

 It also gives off a filament to the knee-joint. 



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

 the lower part of the Adductor magnus, or passes through the opening which 

 transmits the femoral artery, 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 (n. obturatorius accessorius) (Fig. 774) is present 

 in about 29 per cent, of cases. 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 magnus muscle, crosses the ascending ramus of the os pubis, and 

 passes under the outer border of the Pectineus muscle, where it divides into numer- 

 ous branches. One of these supplies the Pectineus, penetrating its deep 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. Occasionally it is very small, and 

 becomes lost in the capsule of the hip-joint. 



The Femoral or Anterior Crural Nerve (n. femvralis) (Figs. 769 and 771) 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 

 fasciae femoris; cutaneous filaments to the front and inner side of the thigh, and 

 to the leg and foot (Fig. 766) ; and articular branches to the hip- and knee-joint. 

 It arises from the second, third, and fourth lumbar nerves, sometimes from the 

 first or fifth as well. It descends through the fibres of the Psoas magnus, emerging 

 from this muscle at the lower part of its outer border, and passes downward be- 

 tween it and the Iliacus muscle, and beneath Poupart's ligament, into the thigh, 

 where it becomes somewhat flattened, and divides into an anterior and a posterior 

 part. Under Poupart's ligament it is separated from the femoral artery by a 

 portion of the Psoas magnus. 



Within the abdomen the femoral nerve gives off from its outer side some small 

 muscular branches to the Iliacus, and a branch to the femoral artery which is 



