84 General Biology 



the ischial symphysis. The anterior head passes through a slit in the 

 adductor magnus and unites with the posterior head in the distal third 

 of the thigh. The tendon of insertion is long and thin, and joins that 

 of the rectus internus minor to be inserted into the tibia just below its 

 head. It adducts the thigh and flexes the leg. 



2. The adductor brevis is a short, wide muscle, lying beneath 

 the upper end of the adductor magnus. It arises from the pubic and 

 ischial symphyses, and is inserted into the preaxial surface of the proxi- 

 mal half of the femur. 



3. The pectineus ( ) is a rather small 

 muscle, lying along the outer (extensor) side of the adductor brevis. 

 It arises from the anterior half of the pubic symphysis in front of the 

 adductor brevis, and is inserted like it into the proximal half of the 

 femur. 



4. The ilio-psoas (iliacus internus) arises by a wide origin 

 from the inner surface of the acetabular portion of the ilium. It turns 

 round the anterior border of the ilium, and crosses in front of the hip- 

 joint, where, for a short part of its course, it is superficial between the 

 heads of the vastus internus and of the rectus anticus femoris. It then 

 passes down the thigh beneath these muscles, and is inserted into the 

 back of the proximal half of the femur. It draws the thigh forward. 



5. The quadratus femoris is a small muscle on the back of the 

 upper part of the thigh ; it arises from the ilium above the acetabulum, 

 and from the base of the iliac crest; it lies beneath the pyriformis and 

 behind the biceps, and is inserted into the inner surface of the proximal 

 third of the femur between the pyriformis and the ilio-psoas. 



6. The obturator is a deeply situated muscle which arises from 

 the whole length of the ischial symphysis and the adjacent parts of the 

 iliac and pubic symphyses, and is inserted into the head of the femur 

 close to the gluteus. 



Innervation: Branches and twigs from sciatic nerve and 

 plexus. 



5. Muscles of the Leg or Shank. 



e. g. (1) Peroneus, a long muscle which arises from the end 

 of the femur, lies along the side of the tibio-fibula, and is inserted into 

 the end of the tibia and the calcaneum ( ). It 



extends the leg and the foot and flexes the foot. 



Innervation : Peroneus nerve. 



(2) Gastrocnemius ( ), a large, spindle- 



shaped muscle which forms the "calf." It arises from the hind side of 

 the end of the femur and tapers into the long tendo Achillis, which passes 

 under the ankle joint and ends in the sole of the foot. It straightens the 

 foot on the shank. 



Innervation : Tibialis nerve. 



