xiii.] THE FROG. 33 r 



The ileo-psoas : it arises from the internal 

 surface of the posterior part of the ilium and is 

 inserted into the posterior aspect of the shaft of 

 the femur. 



. Remove the pyriformis, cut through the semi- 

 membranosus close to its origin and throw it 

 downwards ; this brings into view a small tri- 

 angular muscle 



The quadratus femoris, which arises from the 

 ilium behind the acetabulum and is inserted into 

 the middle of the shaft of the ventral surface of 

 the femur. 



h. The obturatorius : this is a small muscle lying 

 on the dorsal surface of the hip-joint. 



5. The muscles of the leg. 



a. Turn the frog on its back, and remove the skin 

 from the foot : fix the dorsal surface of the foot 

 upwards. The os cruris will now be seen run- 

 ning down the middle of the leg. Lying on its 

 present inner (proper dorsal) side are two mus- 

 cles, viz. 



a. The gastrocnemius : a muscle with a great 

 fleshy belly ; it arises above by two tendons ; 

 one (much the larger) is inserted behind the 

 knee-joint partly into the femur, partly into 

 the os cruris ; the other joins the aponeurosis 

 on the outer side of the knee-joint. Be- 

 low, the muscle ends in a great tendon (tendo 

 Achillis\ which terminates in an aponeurosis 

 on the plantar surface of the foot. 



