474 ^ MANUAL OF ANATOMY 



The obturator ©xternus is somewhat triangular, and is directed 

 at first outwards, and then backwards and upwards. Its round 

 tendon of insertion is closely applied to the back of the neck of the 

 femur, which it slightly grooves in its lower or extracapsular part. 

 The superficial or anterior division of the obturator nerve passes 

 over the upper border of the muscle, and the deep or posterior 

 division pierces the upper part of it. The muscle is in close contact 

 with the lower and back part of the capsular ligament of the hip- 

 joint, a bursa being usually interposed. 



Obturator Nerve. — This nerve is a branch of the lumbar plexus, 

 and generally arises by three roots from the ventral divisions of the 

 second, third, and fourth lumbar nerves, but the root from the second 

 may be absent. For a description of the nerve within the abdo- 

 men and pelvis, see these sections. It escapes from the pelvic 

 cavity by passing through the obturator canal, in which it breaks 

 up into two divisions — superficial or anterior, and deep or posterior. 

 The superficial or anterior division passes over the upper border of 

 the obturator externus, and then descends in front of the adductor 

 brevis, but behind the pectineus and adductor longus. This division 

 communicates with the accessory obturator nerve (when present). 

 The deep or posterior division pierces the upper part of the obturator 

 externus, and then passes behind the adductor brevis and in front 

 of the adductor magnus. 



Branches — Superficial or Anterior Division. — The branches of 

 this division are as follows : articular to the hip- joint, which 

 arises in the obturator canal, and enters the joint through the 

 cotyloid foramen ; muscular to the gracilis, adductor longus, 

 adductor brevis as a rule, and occasionally to the pectineus ; 

 arterial to the coats of the femoral artery ; and cutaneous. 

 This last branch commences at the lower border of the adductor 

 longus, and, after a short course downwards, it pierces the fascia 

 lata between the posterior border of the sartorius and the anterior 

 border of the gracilis, to be distributed to the integument of 

 the inner side of the thigh for a variable extent about the centre. 

 Before this branch pierces the fascia lata it gives one or two twigs 

 which communicate with branches of the long saphenous and the 

 posterior division of the internal cutaneous beneath the sartorius, 

 to form the subsartorial plexus. 



Deep or Posterior Division.— This division furnishes the follow- 

 ing branches : muscular to the obturator externus, adductoiF 

 magnus, and adductor brevis (provided the latter is not suppliecp 

 by the superficial or anterior division) ; and articular to the kneej : 

 joint, called the geniculate branch. This latter branch descends upor i 

 the adductor magnus, which it subsequently pierces close abovM^ 

 the femoral opening, and so reaches the popliteal artery. It accom j^ 

 panies that artery, lying at first on its inner side and then in front ot 

 it, as low as the origin of the central or azygos branch. Here th<' ; 

 nerve leaves the main artery, and passes with its central or azygo,;* 

 branch through the posterior ligament of the knee-joint to th 



