THE POSTERIOR TIBIAL NERVE. 617 



External or short saphenous nerve. — The cutaneous branch of the internal 

 popliteal nerve (ramus communicans tibialis) descends along- the leg beneath the 

 facia, resting on the gastrocnemius, in the furrow between the heads of the 

 muscle, to about mid-way 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 

 poi^liteal nerve (communicans iJeronei). After receiving this communicating 

 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 

 tm-ns forwards beneath the outer malleolus to end m the skin at the side of the 

 foot and on the little toe. On the dorsum of the foot tliis nerve communicates 

 with the musculo-cutaneous nerve. 



In many cases, the external saphenous nerve supplies the outer side of the 

 fourth toe, as well as the little toe. The union between the saphenoiis 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 communication between the nerves is altogether wanting ; in which 

 case the cutaneous nerve to the foot is generally continued from the branch of 

 the internal ijopliteal nerve. 



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 shore 

 distance at the inner side of the vessel and afterwards at the outer 

 side ; the artery inclining inwards from its origin while the nerve 

 continues its straight course. In the interval between the inner mal- 

 leolus 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, after- 

 wards only by the integument and fascia, and it rests upon the deep- 

 seated muscles. 



Lateral branches. — The deep muscles on the back of the leg and 

 the integument of the sole of the foot receive branches from the poste- 

 rior tibial nerve in its course along the leg. 



a. The mtiscnlar hrancJirs emanate from the upper part of the nerve, either 

 separately or by a common trunk ; and one is distributed to each of the deep 

 muscles, viz., the tibialis posticus, the long flexor of the toes, and the long flexor 

 of the gTeat toe. The branch which supplies the last-named muscle runs along 

 the peroneal artery before jaenetrating the muscle. 



h. A calcaneo-jilantar cutaneous branch is furnished from the posterior tibial 

 nerve ; the plantar part perforates the internal annular ligament, and ramifies 

 in the integument at the inner side of the sole of the foot, and beneath 

 the heel. 



Internal Plantar M"erve. — The internal plantar, the larger of the 

 two nerves to the sole of the foot, into which the posterior tibial divides, 

 accompanies the internal or smaller plantar arterj', and supplies nerves 

 to both sides of the three inner toes, and to one side of the fourth. 

 From the point at which it separates from the posterior tibial nerve, 

 it is directed forwards under cover of the first part of the abductor 

 of the great toe, and passing between that muscle and the short 

 flexor of the toes, it gives off the internal cutaneous branch for the 

 great toe, and divides opposite the middle of the foot into three digital 

 branches. The outermost of these branches communicates with the 

 external plantar nerve. 



