3o~ THE SPINAL NERVES. 



which, after supplying filaments to the anterior and posterior tibial arteries, is 

 continued downwards in the membrane to end in the inferior tibio-fibular articu- 

 lation, and the periosteum of the lower part of the tibia ; small Pacinian corpuscles 

 occur on the filaments passing to the bone and ligaments. 



(c) The cutaneous branch. External or short saphenous nerve (n. suralis). The 

 cutaneous branchof the internal popliteal nerve (tibial communicating nerve ; n. cutaneus 

 sunv medialis) (1, 2 s) descends along the leg, in the furrow between the heads of the 



Fi<:. 216. POSTERIOR CUTANEOUS NERVES OF THE LEG. 

 after Hirschfeld and Leveille.) 



(From Sappey, 



1, internal popliteal nerve ; 2, branch to the inner head of the gastro- 

 cnemius muscle ; 3, 4, branches to the outer head and plantaris ; 5, tibial 

 communicating nerve ; 6, external popliteal nerve ; 7, lateral cutaneous 

 branch of the leg ; 8. peroneal communicating branch, descending to unite 

 with the tibial communicating in 9, the external saphenous nerve ; 10, 

 calcaneal branch from this nerve ; 11, calcaneal and plantar cutaneous 

 branches from the posterior tibial nerve ; 12, internal saphenous nerve ; 

 13, posterior branches of this nerve. 



gastrocnemius muscle, to about midway between the knee and 

 the foot. Here it perforates the fascia, and a little lower down 

 is usually joined by a branch from the external popliteal nerve 

 (peroneal communicating}. After receiving this communicat- 

 ing branch, the external saphenous nerve descends beneath 

 the integument near the outer side of the tendo Achillis in 

 company with the short saphenous vein, and turns forwards 

 below the external malleolus to end in the skin on the outer 

 side of the little toe, forming also a communication on the 

 dorsum of the foot with the outer division of the musculo- 

 cutaneous nerve. While turning round the external malleolus, 

 the extern H! saphenous nerve gives off external calcaneal 

 branches to the skin on the outer side of the heel ; and 

 other filaments pass to the ankle-joint and the astragalo- 

 calcaneal articulation (Riidinger), 



Varieties. The union between the tibial communicating 

 nerve and the branch of the external popliteal nerve occurs 

 in some cases higher than usual, occasionally even at or close 

 to the popliteal space. It sometimes happens that the com- 

 munication between the nerves is altogether wanting ; in which 

 case the cutaneous nerve to .he foot is generally continued from 



the branch of the internal popliteal nerve. The area of distribution of the external saphenous 

 nerve in the foot is often increased, so that it supplies in part or wholly the outer one and a 

 half, or even two and a half toes on their dorsal aspect : in these cases the peroneal communi- 

 cating branch is said to be of larger size than usual. Occasionally the external saphenous 

 nerve ends on the outer border of the foot, without reaching the toes. 



Posterior tibial nerve. The internal popliteal nerve receives the name of 

 posterior tibial at the lower margin of the popliteus muscle. It passes down the leg 

 with the posterior tibial artery, lying for a short distance on the inner side of the 

 vessel and afterwards on the outer side, the artery inclining inwards from its origin 

 while the nerve takes a straighter course. In the interval between the inner 

 malleolus and the heel, it divides into the two plantar nerves (internal and external). 

 The posterior tibial nerve, like the accompanying vessels, is covered at first by the 

 muscles of the calf of the leg, afterwards only by the integument and fascia, and it 

 rests upon the deep-seated muscles. 



