2^8 MYOLOGY. 



Posterior Tibial Group. 



For convenience of description, we subdivide the muscles of this 

 group, but the subdivision is a somewhat artificial one, as some^ 

 of the muscles have two actions, flexing one joint and extending 

 another. 



Extensors, 



Gastrocnemius. 

 Plantaris. 



Flexors, 



f Flexor pedis perforatus. 

 Flexor pedis perforans. 

 Flexor pedis accessorius. 

 Popliteus. 



GASTROCNEMIUS. 



{Bifemero-cricaneus.) 

 (PL. III. 38.) 



Situated at the back of the leg, this muscle is somewhat heart- 

 shaped, ending in a flattened tendon ; the fleshy belly is divisible 

 into two portions, and intersected superiorly by strong tendons. 



Origin. — By two heads ; one from a ridge extending upwards 

 from the external condyle in front of the supracondyloid fossa ; 

 the other from the posterior surface of the femur, just above the 

 intercondyloid fossa, and from the internal condyle. 



Insertion, — To the posterior part of the summit of the 

 calcaneum, a synovial bursa being interposed between it and the 

 anterior part, over which it passes. 



Relation, — Anteriorly with the flexor perforatus, popliteus, 

 popliteal vessels and nerves, and the vastus externus above ; 

 posteriorly with the triceps abductor femoris ; internally with 

 biceps rotator tibialis ; superficially with the tibial fascia ; 

 inferiorly the tendon is covered by that of the flexor perforatus, 

 the two forming the Tendo-Acliillis. 



Action. — To extend the tarsal joint. 



r 



