808 THE SERVO US SYSTEM 



subcrureus, the nerve to tlie crureus, the nerve to the vastus externus, and the 

 nen-e to the rectus femoris. They all contain fibres from the third and fourth 

 lumbar nerves. 



(g) The long or internal saphenous nerve accompanies the nerve to thi- 

 vastus internus in its course through Scarpa's triangle, being placed between the 

 latter nerve and the femoral artery. It passes througli Hunter's canal with 

 the femoral artery, lying first to the outer side, then in front, and finally to the 

 inner side of that vessel. At the lower end of the canal it joins the superficial 

 l)ranch of the anastomotic artery which it accompanies, ])etween the posterior border 

 of the sartorius muscle and the anterior border of the gracilis tendon, to the imier 

 side of the knee where it becomes superficial. At this point it approaches the long 

 saphenous vein, and accompanies that vessel for the remainder of its course. It 

 runs down the anterior and inner part of the leg, supplying l;)ranches to the skin of 

 that region, passes in front of the inner malleolus, and suiJi^lies the integument for 

 a))out two inches below tliat prominence. 



As it leaves Hunter's canal, the long saphenous nerve gives ofif a patellar 

 branch. This branch pierces the sartorius, and runs, at first downwards and then 

 outwards, towards the ligamentum patellse. It gives twigs to the integument 

 covering that ligament, and others which curve U2)wards to join the plexus 

 patellne. 



Plexus patellae. — The skin covering the patella is profusely sui)plied with neiTes which 

 commuuicate with one another, and are derived from the external, middle, and internal cutaneous 

 and from the long saphenous. 



Subsartorial plexus. — At the posterior border and partlj- under cover of the sartorius 

 muscle, on the roof of Hunter's canal, and a little below the middle of the thigh, branches of 

 tlie obturator, long saphenous, and internal cutaneous nerves communicate in a plexiform manner 

 and supply the adjacent skin. The posterior branch of the internal cutaneous has an independent 

 distribution, as already described. Occasionally the cutaneous branch of the obturator is unusu- 

 ally large, and may supply an area of integument covering the lower part of the inner hamstring 

 muscles. 



The nerve to the vastus internus accompanies the long saphenous nerve, in 

 Scarpa's triangle, lying to its outer side. At the upper end of Hunter's canal it 

 passes beneath the sartorius, external to the roof of the canal, and enters the inner 

 surface of the vastus internus. It sends down a twig to the knee-joint. 



The nerve to the subcrureus frequently rises from the nerve to the crureus. 

 It passes between the vastus internus and the crureus to the lower third of the 

 thigh, where it supplies the subcrureus and sends a branch to the knee-joint. 



The nerve to the crureus is represented by two or three branches which 

 enter the upper part of the muscle. One of them frequently sends a twig to the 

 knee-joint. 



The nerve to the vastus externus j^asses downwards beneath the rectus and 

 along the anterior border of the vastus externus, accompanied by the descending 

 l)ranch of the external circumflex artery. It also sends a Ijrancli to tlie knee- 

 joint. 



The nerve to the rectus femoris enters the deep surface of that nuiscle, having 

 previously given off a twig to the hip-joint which accompanies the ascending branch 

 of the external circumflex art*^rv. 



