128 TOPOGEAPHICAL ANATOMY OF 



infrequently, fibres of the muscles have origin. As a consequence of 

 the attachment of the septa to the tibia the muscles of the leg are 

 grouped within three fascial compartments: (1) Tibialis anterior and 

 extensor digitorum longus ; (2) perona3us longus ; (3) flexor digitorum 

 longus, flexor hallucis longus, tibialis posterior, and popliteus. Strictly 

 speaking, the popliteal muscle should be regarded as occupying a special 

 compartment of its own. 



The tarsal fascia (fascia tarsi) is attached to the various bony 

 prominences in the region of the tarsus, and blended with the neigh- 

 bouring ligaments. At the back of the tarsus it is particularly strong, 

 forming a bridge from the medial collateral ligament on the one hand 

 to the tuber calcanei and the plantar ligament on the other. The 

 bridge converts the groove formed by the tarsus into a short canal, 

 through which the deep flexor tendon and the plantar vessels and 

 nerves pass to gain the metatarsus. As it passes through the canal, 

 the tendon is provided with a mucous (synovial) sheath. 



In front of the tarsus also the fascia is strong, and here it is 

 connected with the tendon of the long extensor muscle. In this 

 region there are three fascial bands (transverse ligaments), which will 

 be examined in connection with the tendons of the anterior and lateral 

 tibial muscles. 



Dissection. — The fascial investment of the muscles must now be 

 removed. It is well to begin this dissection at the back of the leg. In 

 the hollow bounded posteriorly by the tendon of the gastrocnemius 

 considerable care must be exercised to avoid injury to small vessels. 

 On the medial aspect of the limb in this region the small recurrent 

 tibial artery must be secured as it runs in a proximal direction close to 

 the edge of the gastrocnemius tendon. Risk of destruction of the vessel 

 will be minimised by first disclosing the medial tarsal artery from which 

 it arises. Over the lateral surface of the tuber of the calcaneus the 

 very small lateral tarsal artery is distributed. 



As the dissection proceeds, it will be found necessary to remove the 

 fascial insertions of the biceps and semitendinosus muscles. 



M. GASTROCNEMIUS. — The stroug, tendinous gastrocnemius ^ muscle 

 takes origin from the femur by two heads, each definite and flattened. 

 The lateral head (caput laterale) arises from the margin of' the plantaris 

 fossa, while the medial head (caput mediale) springs from a rough 

 elevated area on the medial lip of the linea aspera at the same level 

 as the fossa. Through the gap between the two heads the popliteal 

 vessels and the tibial nerve gain the leg. The two heads soon join to 

 form a common fleshy belly, which tapers to a strong rounded tendon 

 about the junction of the proximal and middle thirds of the tibia. 



The tendon of the gastrocnemius (tendo calcaneus Achillis) is very 



' yasTYip (gaster) [Gr.], belly. Kvniir] (cneme) [Gy.\ the leg. 



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