726 THE NEKVOUS SYSTEM. 



third of the thigh on the medial side. It supplies the skin of the distal half of 

 the thigh, extending as far as the knee, where it joins in the formation of the 

 patellar plexus. 



The distal branch represents the termination of the nerve. It passes along the 

 medial side of the thigh over the sartorius muscle, and communicates in the 

 middle third of the thigh with the saphenous and obturator nerves to form the 

 obturator plexus. Piercing the fascia lata on the medial side of the thigh in the 

 distal third, it ramifies over the side of the knee, and assists in the formation of 

 the patellar plexus. 



The size of the medial cutaneous nerve varies with the size of the cutaneous 

 part of the obturator, and of the saphenous nerve. 



N. Saphenus. The saphenous nerve may be regarded as the terminal branch 

 of the femoral nerve. It is destined for the skin of the leg and foot. From its 

 origin in the femoral triangle it extends distally alongside the femoral vessels to 

 the adductor canal. In the canal it crosses obliquely over the femoral sheath 

 from lateral to medial side. At the distal end of the canal, accompanied by the 

 saphenous branch of the arteria genu suprema, it passes over the tendon of the 

 adductor magnus, and opposite the medial side of the knee-joint becomes cutaneous 

 by passing between the sartorius and gracilis muscles. The nerve then extends 

 distally in the leg along with the great saphenous vein, and coursing over the front 

 of the medial malleolus it terminates at the middle of the medial border of the foot. 



Branches. 1. A communicating branch arises in the adductor canal, and, 

 passing medially behind the sartorius, joins with branches of the obturator nerve 

 in forming the obturator plexus. 



2. Ramus Infrapatellaris. The infra-patellar branch arises at the distal end of 

 the adductor canal, and piercing the sartorius muscle is directed distally and 

 forwards below the patella, and over the medial condyle of the tibia to the front 

 of the knee and proximal part of the leg. It enters into the formation of the 

 patellar plexus. 



3. An articular branch sometimes arises from the nerve at the medial side of 

 the knee. 



4. Rami Cutanei Cruris Mediales. The terminal branches of the saphenous nerve 

 are distributed to the skin of the front and medial side of the leg and the 

 posterior half of the dorsum and medial side of the foot. 



Plexus Patellaris. The patellar plexus consists of fine communications 

 beneath the skin in front of the knee, between the branches of the cutaneous 

 nerves supplying that region. The nerves which enter into its formation are 

 the infra-patellar branch of the saphenous, medial and intermediate cutaneous 

 nerves, and sometimes the lateral cutaneous nerve of the thigh. 



The accessory obturator nerve (n. obturatorius accessorius) is only occasionally present (29 

 per cent., Eisler). It arises from the third, or third and fourth lumbar nerves, between the roots 

 of the obturator and femoral nerves. Associating itself with the obturator, from which, however, 

 it is quite separable, it appears in the abdomen at the medial side of the psoas muscle, and 

 coursing over the pelvic brim behind the external iliac vessels, it leaves the obturator nerve, and 

 enters the thigh in front of the os pubis. 



In the thigh, behind the femoral vessels, it usually ends in three branches : a nerve which 

 replaces the branch from the femoral nerve to the pectineus, a nerve to the hip-joint, and a 

 nerve which communicates with the superficial part of the obturator nerve. In some cases it 

 only supplies the nerve to the pectineus ; more rarely it is of considerable size, and reinforces the 

 obturator nerve in the inner vation of the adductor muscles. 



The accessory obturator nerve was first described by Winslow as the n. accessorius anterioris 

 cruralis. Schmidt later described it in great detail, and gave it the name it now bears. It is 

 more closely associated with the femoral than with the obturator. Its origin is behind the roots 

 of the obturator : it is separated, like the femoral, from the obturator by the pubic bone, and 

 its chief branch, to the pectineus muscle, replaces the normal branch from the femoral nerve. 

 On the other hand, for a part of its course it accompanies the obturator, and in rare cases it 

 may replace branches of that nerve. 



