606 DISSECTION OF THE LEG. 



knee. In the centre of the leg lies the external saphenous vein, with the 

 small sciatic nerve as its companion above, and the external saphenous 

 nerve below the middle of the leg. On the outer side, in the upper third, 

 cutaneous offsets of the external popliteal nerve will be met with. 



The superficial fascia^ or the fatty layer of the back of the leg, is least 

 thick over the tibia. Over the line of the superficial vessels it may be 

 separated into two layers. 



SUPERFICIAL VEINS. Two veins appear of the dissection of the back 

 of the leg, which are named saphenous inner and outer. 



The internal saphenous vein (fig. 208, d) begins in an arch on the 

 dorsum of the foot. Ascending along the leg in front of the inner ankle, 

 and then behind the inner edge of the tibia, it reaches the thigh (p. 555). 

 In the leg the vein is joined by superficial branches, and by deep roots 

 from the tibial veins. 



The external saphenous vein (fig. 207, c) begins at the outer end of the 

 arch on the dorsum of the foot, and appears below the outer ankle. The 

 vein then courses along the back of the leg to the ham, where it ends in 

 the popliteal vein. It receives large branches about the heel, and others 

 on the back of the leg, communicating with the internal saphenous. 



Cutaneous arteries accompany the superficial veins and nerves of the 

 leg. 



CUTANEOUS NERVES (fig. 207). The nerves in the fat of the back of 

 the leg are prolongations of branches already examined in part, viz. the 

 internal and external saphenous, external popliteal, small sciatic, and in- 

 ternal cutaneous of the thigh. 



The internal saphenous nerve (fig. 207, T ) accompanies the vein of the 

 same name beyond the knee (p. 573), and terminates at the middle of the 

 inner border of the foot. In the leg the nerve gives off lateral cutaneous 

 offsets, and the outer of these turn over the tibia to the anterior aspect. 



The external saphenous nerve (207, 5 ) is a branch of the internal pop- 

 liteal. Perforating the deep fascia about the middle of the leg, it is con- 

 tinued with the external saphenous vein below the outer ankle, and is 

 distributed to the outer side of the foot and little toe. As soon as the 

 nerve enters the fat it is joined by the communicating branch of the ex- 

 ternal popliteal ; and near the heel it gives large and long brandies to 

 the integuments. 



Cutaneous nerves of the external popliteal. One branch of the external 

 popliteal trunk, viz., communicating peroneal (fig. 207, 4 ), joins the external 

 saphenous nerve about the middle of the leg ; but not uncommonly this 

 branch extends as a distinct nerve as far as the heel. One or two other 

 small cutaneous offsets of the external popliteal terminate over the fore 

 part and outer side of the leg in the upper half. 



The small sciatic nerve (fig. 207, 6 ) perforates the fascia near the pop- 

 liteal space, and reaches to about the middle of the leg with* the external 

 saphenous vein : it ramifies in the integuments, and joins the external 

 saphenous nerve. 



Offset of the internal cutaneous (fig. 207, 8 ). The inner branch of the 

 internal cutaneous of the thigh (p. 550) extends to the middle of the leg, 

 and communicates with the internal saphenous nerve. 



Dissection. The deep fascia will be seen by removing the fat. The 

 superficial vessels and nerves may be either cut or turned aside. 



The special or deep fascia on the posterior aspect of the leg covers the 

 muscles, and sends a thick process between the deep and superficial layers. 



