THE LUMBAR PLEXUS. 



1329 



Fig. 



nil. 



Anterior 



IHacus. 

 crural nerve. 



The branch to the rectus femoris usually splits into three twigs, which separately enter the 

 posterior surface of their muscle. It furnishes fine twigs to the antero-lateral portion of the 

 capsule of the hip joint. 



The branch to the vastus externus passes over the rectus and, in company with the 

 descending branch of the external circumflex artery, reaches the vastus externus, whose 

 anterior margin it enters in a series of twigs. It sends a branch down to the knee joint. 



The nerves to the crureus number usually either two or three. The upper branch is usually 

 the shortest and passes directly to the anterior surface of the crureus, where it penetrates the sub- 

 stance and supplies the upper 

 portion of the muscle. A sec- 

 ond branch pierces the vastus 

 internus and passes down- 

 ward under the anterior bor- 

 der of that muscle. It sup- 

 plies the lower portion of the 

 crureus, the subcrureus, the 

 periosteum of the lower an- 

 terior part of the femur and 

 the capsular ligament of the 

 knee joint. A third branch is 

 distributed to the lateral por- 

 tion of the crureus and by 

 means of its terminal filaments 

 aids in the innervation of the 

 knee joint. 



The branch to the vastus 

 internus accompanies the in- 

 ternal saphenous nerve along 

 the inner side of the vastus 

 internus, under cover of the 

 strong aponeurosis which 

 forms the roof of Hunter's 

 canal. It sends filaments to 

 the upper part of the vastus 

 internus and then enters that 

 muscle about the middle of 

 the thigh. Its continuation 

 accompanies the deep branch 

 of the anastomotica magna 

 artery and supplies the cap- 

 sule of the knee joint. 



b b . The articular 

 branches (rr. articulares) 

 supply the hip and knee 

 joints. Those filaments which 

 are destined for the hip are 

 derivatives of the branch to 

 the rectus femoris. Those 

 which aid in the innervation 

 of the knee arise from the in- 

 ternal saphenous and from 

 the nerves to the vasti exter- 

 nus and internus and the 

 crureus. 



cc. The internal or long 

 saphenous nerve (n. saphenus) 

 (Fig. 1 109) is the continuation 

 of the posterior division of 

 the anterior crural nerve. It 

 courses down the thigh 

 first lateral to and then an- 

 terior to the superficial femoral artery under cover of the sartorius muscle. At the apex 

 of Scarpa's triangle it enters Hunter's canal and accompanies the vessels therein contained as 

 far as the opening in the adductor magnus. Departing from the vessels at this point, the nerve, 

 piercing the anterior wall of Hunter's canal, continues a downward course between the vastus 



Rectus femoris, cuW 



Femoral vein' 



Nerve to pectineus' 



Femoral artery 



Articular branch 



Nerve to rectus 



Ext. circumflex artery. 



Middle cutaneous, 

 nerve 

 Rectus femoris, cut 



A descending branch 

 of ext. circumflex art. 



Nerve to vastus 

 internus 



Nerve to crureus 

 Crureus- 



Pubic bone 

 1-Pectineus 



Adductor 

 longus 



-rj— Adductor 

 magnus 



Int. saphenous 



nerve 

 Post. div. int. 

 cutaneous 

 nerve 



Aponeurotic 

 roof of Hunt- 

 er's canal 



A br. of int. sa- 

 phenous ner\'e 



A muscular br. 

 of femoral 

 artery 



Vastus 

 internus 



Internal saphenous nerve 



Superficial br. anasto- 

 motica magna art. 



Tendon of adductor 

 magnus 



Dissection of right thigli, showing relation of anterior crural nerve 

 to blood-vessels and to Hunter's canal. 



84 



