POSTERIOR TIBIO-FIBULAR REGION. 



421 



POSTERIOR TIBIO-FIBULAR EEGION. 



Dissection (Fig. 256). Make a vertical incision along the middle line of the back of the leg, 

 from the lower part of the popliteal space to the heel, connecting it below by a transverse in- 

 cision extending between the two malleoli ; the flaps of integument being removed, the fascia 

 and muscles should be examined. 



?ig. 259. Muscles of the Back of tho 

 Leg. Superficial Layer. 



The muscles in this region of the leg are 

 subdivided into two layers, superficial and 

 deep. The superficial layer constitutes a 

 powerful muscular mass, forming the calf of 

 the leg. Their large size is one of the most 

 characteristic features of the muscular appa- 

 ratus in man, and bears a direct connection 

 with his ordinary attitude and mode of pro 

 gression. 



Superficial Layer. 



Gastrocnemius. Soleus. 



Plantaris. 



The Gastrocnemius is the most superficial 

 muscle, and forms the greater part of the 

 calf. It arises by two heads, which are con- 

 nected to the condyles of the femur by two 

 strong flat tendons. The inner head, the 

 larger, and a little the more posterior, arises 

 from a depression at the upper and back 

 part of the inner condyle. The outer head 

 arises from the upper and back part of the 

 external condyle, immediately above the 

 origin of the Popliteus. Both heads, also, 

 arise by a few tendinous and fleshy fibres 

 from the ridges which are continued upwards 

 from the condyles to the linea aspera. Each 

 tendon spreads out into an aponeurosis, 

 which covers the posterior surface of that 

 portion of the muscle to which it belongs ; 

 that covering the inner head being longer 

 and thicker than the outer. From the ante- 

 rior surface of these tendinous expansions, 

 muscular fibres are given off. The fibres in 

 the median line, which correspond to the 

 accessory portions of the muscle derived 

 from the bifurcations of the linea aspera, 

 unite at an angle upon a median tendinous 

 raphe below ; the remaining fibres converge 

 to the posterior surface of an aponeurosis 

 which covers the front of the muscle, and 

 this, gradually contracting, unites with the 

 tendon of the Soleus, and forms with it the 

 tendo Achillis. 



Relations. By its superficial surface, with 

 the fascia of the leg, which separates it from 

 the external saphenous vein and nerve. By 

 its deep surface, with the posterior ligament of the knee-joint, the Popliteus, So- 

 leus, Plantaris, popliteal vessels, and internal popliteal nerve. The tendon of the 

 inner head corresponds with the back part of the inner condyle, from which it 





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* MI'II 



