66 THE MUSCULAR SYSTEM OF THE FROG 



V. The ciuadralaiS' femoris is a small muscle on the 

 back of the iopper pa;tt of/1.Se thigh: ib arises 

 from theiUipn abovef me acetabulum, a^d from 

 the bas^' of the iliao' crest -Jit li/^ her^e&th. the 

 pyrifor*(4a''and behirid the ^cepSj and Js/tnserted 

 into the piner Surface of the proximal third of 

 the f enivp betat^eefa the pyrifonnis and the ilio- 

 psoas' ■ ,' / / / 

 vi. The o^ui&tOF is a deeply situated muscle which 

 arises 'fi|oij/tiJ'6 whole length of the ischial sym- 

 phisis and the/jidjacent pdocts of/ the Uiac and 

 pwoic symphys&B, and is injferted into the head 

 of the femur close to the glutseus. 

 2. Muscles of the leg. 

 As in the thigh, we distinguish extensor and flexor surfaces, 



corresponding to the front and back of the leg in man ; and also 



preaxial and postaxial surfaces, corresponding to the inner and 



outer sides of the human leg. 



Lay the frog on its belly amd commence the dissection from the 



postaxial swface. 



"H" 1. The gastrocnemius is the large muscle forming the 

 calf of the leg : it has two heads of origin, of 

 which the larger aris es by a s-trong, flattened 

 tendon from thef Sexoi^ surface of the distal end 

 of the([ £gmu^ , wEile the smaller head, which 

 joins the main muscle about one-fourth of its 

 length below the knee, arises from the edge of 

 the tendon of the triceps extensor femoris where 

 it covers the knee. The muscle is thickest in 

 its upper third, and taperinp f posteriorly ends in 

 the strong ^iSnflo Acliillis,^hich passes under 

 the ankle-johitj) buiug lUTichthickened as it does 

 so, and ends in the strong plantar fascia of the 

 foot, 

 ii. The, tibialis posticus, arises from th^ whole length 

 of the flexor siirfape of the tibia : it ends in a 

 1/endon which passes round th^ inner malleolus, 

 lying in a groove in the lower end ofi thje tibia, 

 and is inserted into the dorsal surfii«e of the 

 astragalus. 



