222 ELEMENTARY BIOLOGY. [XIII. 



/. Divide and reflect the vastus externus and the 

 biceps : beneath them will be laid bare — 



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. 



g. Eemove 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 ohturatorius: 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 running 

 down the middle of the leg. Lying on its present 

 inner (proper dorsal) side are two muscles, 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-joLat. Below, 

 the muscle ends in a great tendon {tendo 

 Achillis), which terminates in an aponeurosis 

 . on the plantar surface of the foot. 



