42 LABORATORY DIRECTIONS 



31. PoPLiTEUs. — The short triangular muscle behind the 

 knee, near the proximal end of the flexor digitorum longus, is the 

 popliteus. It originates by a strong tendon from the lateral side 

 of the femur; its fibers diverge obliquely and are inserted on the 

 medial side of the proximal end of the tibia. 



Action: to rotate the shank. 



32. Tibialis Posterior. — This is a slender muscle com- 

 pletely covered by the flexor digitorum longus. It originates 

 from the head of the fibula and from the tibia near its head. 

 About half way down the tibia it passes into a tendon, which 

 passes through a groove on the distal end of the tibia and inserts 

 on the scaphoid and medial cuneiform bones. 



Action: to extend the foot. 



33. Extensor Digitorum Longus. — On the dorsal side of 

 the foot is a tendon with four branches going to the toes. Trace 

 this tendon back through a small ligament on the foot to a 

 muscle which passes under the large transverse ligament just 

 above the ankle. This is the extensor digitorum longus which 

 should be separated from the large muscle lying between it and 

 the tibia. The extensor digitorum longus originates by a 

 tendon from the lateral side of the distal end of the femur. 

 Insertion is on the upper surface of each digit. 



Action: to extend the toes and flex the foot. 



34. Tibialis Anterior. — This is the long muscle between 

 the extensor digitorum longus and the tibia, already partly 

 dissected. It originates from the proximal portions of both 

 tibia and fibula and inserts by a tendon on the first metatarsal. 

 The tendon, together with the extensor digitorum longus muscle, 

 is held down by the transverse ligament. 



Action: to flex the foot. 



35. Peroneus Longus. — ^There now remain three peroneus 

 muscles on the lateral side of the shank, between the extensor 

 digitorum longus and the flexor hallucis longus. The peroneus 

 longus is the outermost of these muscles. It originates from the 

 proximal half of the fibula; and soon passes into a tendon, which 

 continues through a groove on the distal end of the fibula and 

 inserts on the proximal parts of all the metatarsals. 



Action: to flex the foot. 



