166 THE NERVOUS SYSTEM 



extremity of the inguinal ligament, behind which it passes 

 to enter the thigh. As it lies on the iliacus, it is placed 

 behind the caecum, on the right side, and the iliac colon, on 

 the left side of the body. It supplies the skin of the lateral 

 aspect of the thigh and extends as far as the knee-joint. In 

 addition, it gives off branches, which pass backwards to the 

 buttock and back of the thigh. 



The Femoral Nerve (Anterior Crural) (L. 2.3.4.) is the 

 biggest and most important branch of the lumbar plexus. 

 It enters the thigh behind the inguinal ligament, in the groove 

 between the psoas major and the iliacus, but it supplies the 

 latter muscle before it leaves the pelvis. 



In the thigh, it gives off (a) Motor branches^ which supply 

 the quadriceps femoris, the sartorius and the pectineus; 

 (b) articular branches to the hip- and knee-joints ; and (c) the 

 medial and intermediate cutaneous nerves of the thigh and the 

 saphenous nerve. 



The Quadriceps Femoris comprises the Rectus Femoris, the Vastus 

 Medialis, Vastus Intermedius (Crureus) and the Vastus Lateralis. 



The Rectus Femoris arises from the antero-inferior spine of the ilium 

 and is inserted into the proximal border of the patella. It acts as a flexor 

 of the hip and as an extensor of the knee. Consequently, it forms a 

 prominent elevation on the front of the thigh, when the hip-joint is 

 flexed and the knee-joint extended, the limb not being supported. 



The three Vasti muscles arise from the femur and are inserted into the 

 patella. The Medialis and Lateralis form distinct prominences at the 

 sides of the knee, when they are called on to keep the leg extended 

 against gravity ; the elevation produced by the medialis extends more 

 distally than that produced by the lateralis. 



The Sartorius arises from the antero-superior spine of the ilium and 

 passes distally and medially to reach the medial side of the thigh. It 

 then descends vertically across the medial aspect of the knee-joint and 

 is inserted into the proximal part of the antero-medial surface of the tibia. 

 It acts as a flexor of both the hip- and the knee-joints, and it can be made 

 to stand out when the lower limb, flexed at both joints, is elevated from 

 the ground. Since the sartorius is supplied by the femoral nerve, its 

 action as a flexor of the knee is of special interest (p. 175). 



The Pectineus lies in the proximo-medial part of the thigh. It arises 

 from the superior ramus of the pubis and is inserted into the posterior 



