The Frog 85 



(3) Tibialis anticus, arising from the front of the femur by a 

 long tendon, lies in front of the shank and divides into two bellies, 

 which are respectively inserted into the astragalus and calcaneus. It 

 bends the foot on the shank. 



Innervation : Peroneus nerve. 



(4) Tibialis posticus arises from the whole length of the flexor 

 surface of the tibia. It ends in a tendon which passes round the inner 

 malleolus ( ), lies in a groove in the lower end of 

 the tibia and is inserted into the dorsal surface of the astragalus. It 

 extends the foot when flexed, and flexes the foot when extended. 



Innervation : Tibialis nerve. 



(5) Extensor cruris lies along the preaxial side of the tibialis 

 anticus partly covered by this and partly by the strong fascia of the 

 leg. It arises by a long tendon from the preaxial condyle of the femur, 

 runs in a groove in the upper end of the tibia, and is inserted into the 

 extensor surface of the tibia along nearly its whole length. It extends 

 the foot. 



Innervation : Tibialis nerve. 



6. Muscles of the Foot. 



These, just as the muscles of the wrist and hand are many and 

 complicated, but the student should know at least the general location of 

 the following: 



Aponeurosis plantaris. 



The flattened and broadened continuation of the tendon of the 

 gastrocnemius muscle passing over the heel and spreading out on the 

 sole of the foot in a sort of triangle with the base toward the toes. 

 Where the aponeurosis crosses the heel it is. known as the tendon of 

 Achilles. 



Flexor digitorum I, II, III, IV, V. 



Each digit usually has a flexor, extensor, abductor, and ad- 

 ductor bearing the number of the toe to which it is attached, the great 

 toe being I. 



There are also small interosseus muscles between the various 

 tarsal bones. 



For a detailed account of all muscles of the frog see : Ecker's 

 "The Anatomy of the Frog." (Oxford University Press.) 



REPRODUCTIVE ORGANS 



The sexes are separate in the frog. The male has a rather thick pad 

 on the underside of its thumb, larger in the spring, at the breeding sea- 

 son, than at any other time of the year. The two rounded or oval 

 spermaries (A, Fig. 25), of a light yellow color, are found at the upper 



