1060 



THE NERVE SYSTEM 



The articular branches (rami articulares), usually three in number, supply the 

 knee-joint; two of these branches accompany the superior and inferior internal 

 articular arteries, and a third, the azygos articular artery. 



The muscular branches (rami musculares), four or five in number, arise from the 

 nerve as it lies between the two heads of the Gastrocnemius ; they supply that 

 muscle and the Plantaris, Soleus, and Popliteus. The branch which supplies 

 the Popliteus turns around its lower border and is distributed to the deep surface 

 of the muscle. 



The communicans tibialis (n. cutaneus surae medialis) descends between the two 

 heads of the Gastrocnemius, and about the middle of the back of the leg pierces 

 the deep fascia, and joins a communicating branch (ramus anastomoticus pero- 

 naeus) from the external popliteal nerve to form the short or external saphenous 

 nerve (Fig. 776). The external saphenous nerve, formed by the communicating 

 branches of the internal and external popliteal nerves, passes downward and out- 

 ward near the outer margin of the tendo Achillis, lying close to the external saphe- 

 nous vein, to the interval between the external malleolus and the os calcis. It 

 divides into two branches, the posterior of which breaks up into lateral calcaneal 

 branches (rami calcanei laterales). The anterior branch (n. cutaneus dorsalis 

 lateralis) winds around the outer malleolus, and is distributed to the integument 

 along the outer side of the foot and little toe, communicating on the dorsum of 

 the foot with the musculocutaneous nerve. In the leg its branches communicate 

 with those of the small sciatic. The cutaneous area supplied by the external 

 saphenous nerve is indicated in Fig. 778. 



The Posterior Tibial Nerve (Fig. 776), the direct continuation of the internal pop- 

 liteal nerve, commences at the lower border of the Popliteus muscle, and passes 

 along the back part of the leg with the posterior tibial vessels to the interval 

 between the inner malleolus and the heel, where it divides into the external and 

 internal plantar nerves. It lies upon the deep muscles of the leg, and is covered 

 above by the muscles of the calf, lower down by the skin and fascia. In the 

 upper part of its course it lies to the inner side of the posterior tibial artery, but it 

 soon crosses that vessel, and lies to its outer side as far as the ankle. In the lower 

 third of the leg it is placed parallel with the inner margin of the tendo Achillis. 



The branches of the posterior tibial nerve are muscular, internal calcaneal, and 

 articular. 



The muscular branches (rami musculares) arise either separately or by a common 

 trunk from the upper part of the nerve. They supply the Soleus, Tibialis pos- 

 ticus, Flexor longus digitorum, and Flexor longus hallucis muscles; the branch 

 to the latter muscle accompanies the peroneal artery. The branch to the Soleus 

 enters the deep surface of the muscle, while that from the internal popliteal enters 

 the superficial surface. 



The internal calcaneal branches (rami calcanei mediates) perforate the internal 

 annular ligament, and supply the integument of the heel and inner side of the foot 

 ' (Fig. 778). 



The articular branch (ramus articularis ad articulationem talocruralem) is given 

 off just above the bifurcation of the nerve and supplies the ankle-joint. 



The Internal Plantar Nerve (n. plantaris medians') (Fig. 777), the larger of the 

 two terminal branches of the internal popliteal, accompanies the internal plantar 

 artery along the inner side of the foot. From its origin at the inner ankle it passes 

 beneath the Abductor hallucis, and then forward between this muscle and the 

 Flexor brevis digitorum ; it divides opposite the bases of the metatarsal bones into 

 four plantar digital branches (nn. digitales plantares communes') and communicates 

 with the plantar nerve. 



Branches. In its course the internal plantar nerve gives off cutaneous branches, 

 which pierce the plantar fascia and supply the integument of the sole of the foot 



