36o ZOOTOMY. 



In the shank and foot. 



457. The tibialis anticus (Figs. 67, 68, and 69, tb.a)^ 

 forming the anterior border of the shank : it arises from 

 the outer tuberosity of the tibia and from its cnemial 

 crest, and is continued distally into a long tendon, which 

 passes under a strong annular ligament (an.l) placed 

 obliquely at the distal end of the anterior surface of the 

 femur : entering the foot the tendon of the tibialis anticus is 

 inserted into the proximal end of the second (apparent first) 

 metatarsal : divide and reflect, first separating carefully from 

 the next muscle. 



458. The extensor communis digitorum {ex.c.d), 

 situated between the tibia and the tibialis anticus, and 

 closely applied to the latter : it arises by a long tendon from 

 the anterior surface of the distal end of the femur just 

 external to the intercondylar notch : to see this origin the 

 tendon must be traced through the capsule of the knee- 

 joint (§ 474) : distally the muscle divides into four tendons, 

 which pass through the annular ligament, then through a 

 similar but smaller loop on the dorsal surface of the carpus, 

 and are inserted into the phalanges of the four digits in the 

 same manner as the corresponding muscle of the hand 

 (§ 416) : divide and reflect. 



459. The extensor digiti primi (properly secondi) 

 (ex.d.i), arising from the inner tuberosity of the tibia, and 

 passing along the inner aspect of the crus, at about the 

 middle of which it becomes tendinous : this tendon runs in 

 a groove on the pre-axial side of the distal end of the tibia, 

 beneath (ventral to) the curved proximal end of the second 

 metatarsal, curves over to the dorsal side of the latter, and 

 unites with the first tendon of the common extensor on the 

 dorsal surface of the proximal phalanx : divide and reflect. 



460. The gastrocnemius (^p), a large two-headed 



