366 THE INFERIOR EXTREMITY 



tendo calcaneus, where it joins with the medial cutaneous 

 nerve of the calf in the formation of the sural nerve. It 

 supplies the skin of the proximal two-thirds of the posterior 

 surface of the calf. 



N. Suralis. The sural nerve is formed, by the union of 

 the anastomotic branch of the peroneal nerve and the medial 

 cutaneous nerve of the calf, in the superficial fascia at the 

 level of the proximal end of the lateral border of the tendo 

 calcaneus. It descends, alongside of the small saphenous 

 vein, behind the lateral malleolus ; then it turns forwards, below 

 the lateral malleolus, to the lateral border of the dorsum of 

 the foot ; there it gives a communicating twig to the branch of 

 the superficial peroneal nerve which is distributed in the 

 adjacent sides of the fourth and fifth toes, and then continues 

 forwards to the lateral part of the dorsum of the little toe. 

 In the region of the dorsum of the foot it is known as the 

 lateral dorsal cutaneous nerve of the foot, a superfluous and 

 unnecessary term. 



The medial cutaneous nerve of the thigh, the posterior 

 cutaneous nerve of the thigh, and the lateral cutaneous 

 nerve of the leg have already been sufficiently described 

 (see pp. 257, 306, 315). 



Dissection. After the cutaneous veins and nerves of the 

 posterior region of the leg have been studied, remove the remains 

 of the fatty superficial fascia, and clean the deep fascia which 

 lies subjacent to it. 



Deep Fascia. In the proximal part of the calf the deep 

 fascia is thin and transparent ; it thickens considerably as 

 the region of the heel is approached. In no part of its 

 extent is it very dense, but as it passes from the back of the 

 leg to the medial side of the ankle, and covers the interval 

 between the medial malleolus and the calcaneus, it is greatly 

 strengthened to form the ligamentum laciniatum (O.T. 

 internal annular ligament), whilst at the lateral side of the 

 ankle it is also thickened to form the peroneal retinacula 



(P- 339)- 



It is continuous proximally with the popliteal fascia, and, a 



short distance distal to the knee on the medial side, it receives 

 reinforcements of fibres from the tendons of the sartorius, 

 gracilis, and semitendinosus. Distally, on the medial side, it 

 is continuous with the ligamentum laciniatum (O.T. internal 



