THE LOWER LIMB 475 



interior of the articulation. The geniculate nerve is frequently 

 absent. 



Accessory Obturator Nerve.— This nerve is present in about 30 per 

 cent, of bodies. It is comparatively small in size, and arises by 

 two roots from the anterior primary divisions of the third and 

 fourth lumbar nerves, the roots being interposed between those of 

 the anterior crural and obturator nerves. It descends along the 

 inner border of the psoas magnus, close to the brim of the pelvis, 

 imderneath the external iliac vessels. It then passes over the 

 superior pubic ramus, where it passes beneath the pectineus, and 

 so emerges on to the thigh beneath Poupart's ligament. Under 

 cover of the pectineus it divides into the following three branches : 

 (i) articular to the hip- joint ; (2) muscular to the deep surface of 

 the pectineus ; and (3) a reinforcing branch to join the superficial 

 or anterior division of the main obturator nerve. 



Scarpa's Triangle. — ^This triangle is situated on the front of the 

 thigh below Poupart's ligament. The base, which is directed 

 upwards, is formed by Poupart's hgament. The outer boundary 

 is formed by the inner border of the sartorius in its upper fourth, 

 and the inner boundary is constructed by the internal border of 

 the adductor longus in its upper part. The apex is about 3^ inches 

 below Poupart's ligament, and is formed by the overlapping which 

 there takes place between the superficially placed sartorius and the 

 more deeply placed adductor longus. The roof is formed by the 

 skin, two layers of the superficial fascia, and fascia lata. The 

 following structures also he in the roof; the femoral branch of 

 the genito-femoral nerve; the inguinal and superficial femoral or 

 saphenous glands ; the cutaneous branches of the common femoral 

 artery (except the inferior external pudic), with their correspond- 

 ing veins ; the saphenous opening ; and the terminal part of the 

 long saphenous vein, with the anterior and posterior saphenous 

 veins joining it. The floor contains the following muscles, in 

 order from within outwards : adductor longus ; pectineus ; psoas 

 magnus ; and iliacus (the latter two being here united to form 

 one muscle, called the ilio-psoas). Occasionally a small part of 

 the adductor brevis is seen between the adductor longus and 

 pectineus, and, when this is so, the superficial or anterior division 

 of the obturator nerve may be seen in part. 



Contents. — ^The contents are as follows : the common femoral 

 artery and its branches ; the first part of the superficial femoral 

 artery and its branches ; the upper part of the femoral vein and 

 its tributaries ; and the anterior femoral nerve, with its divisions 

 and their branches. 



Hunter's Canal.* — ^This is a somewhat triangular, musculo- 

 aponeurotic canal, which occupies the middle two- fourths of the 

 thigh on its inner aspect. 



* The canal has received this complimentary name because John Hunter was 

 the first surgeon who tied the superficial femoral artery in this part of its course 

 for popliteal aneurism in the year 1785. 



