226 THE BIOLOGY OF THE ANIMAL 



I sus. Separate the rectus internus and the ad- 

 ductor magnus, and find between them 



*. The semitendinosus, a muscle with two heads. 

 Divide the sartorius transversely and find 



j. The adductor brevis, whose head lies between 

 the sartorius and the adductor magnus. 



Tc. The pectineus, lying along the outer margin of 

 the adductor brevis. 



Push aside the vastus internus and find 



I. The ilio-psoas, lying dorsally from the adductor 



brevis. 

 m. The quadratus femoris, posterior to the 



gluteus. 



n. The obturator, towards the median line from 

 the quadratus femoris. 



Which of the above-named muscles pull {jlex) 

 the thigh ? Which draw {extend) it backward ? 

 On the leg find 



o. The gastrocnemius, the muscle of the calf of the 

 leg. Note its large tendon, the tendo Achillis. 



p. The tibialis anticus, along the outer margin of 

 the leg. 



^. The tibialis posticus, lying along the inner 

 margin of the gastrocnemius. 



r. The peroneus, lying between the tibialis anticus 

 and the gastrocnemius. 



s. The extensor cruris brevis, along the anterior 

 margin of the tibialis anticus. 



Examine the muscles and tendons of both sur- 

 faces of the foot. 



Which of the leg muscles are extensors ? Flex- 



