The majority of the muscular branches arise from the posterior part of the trunk, and we observe, first, two branches for the two heads of the gastrocnemius entering their an terior surface. The inner branch arises fre quently from a trunk common to it and the tibial saphxnus ; the outer, from a trunk com mon to it and a large branch for the solxus, which enters, usually, the posterior surface of that muscle. When the outer branch is small, one or two others are given off lower down, to enter its anterior aspect. The small branch for the plantaris is derived, in the majority of in stances, from the trunk of the tibial ; but sometimes from the inferior internal articular nerve.
The nerve for the poplibous, given off' op posite the knee-joint, is directed forwards to the poplitxal vessels, descends external to thein, and terminates at the lower border of the muscle by entering its substance.
The nerve to the tibialis posticus comes off from the above, descends along the back of the muscle, gives numerous filaments to it, and terminates by entering below the middle.
The nerve for the flexor comnzunis digitorunz and the longus pollicis take their origin together somewhat below the preceding ; that for the latter muscle being the larger, and descend ing to within a short distance of the ankle joint, in company with the fibular artery. The articular branches are three in number, and correspond with the internal and anterior articular branches of the poplitmal artery.
" The superior internal articular, very small, arises above the articulation, descends on the outer side of the poplitmal vessels, passes beneath them, and runs with its artery to the front of the femur and inner part of the ar ticulation ; this is the least constant of the branches. The inferior internal articular, the largest of the nerves to the joint, arises rather above the articulation, descends to it, lying external to the vessels, is then directed in wards, beneath the poplitmal vessels, and meets with the artery of the same name ; it now lies on the poplitseus, covered by the fascia, passes beneath the internal lateral liga ment, winds round the head of the tibia, per forates the capsule, and supplies the synovial membrane. This branch gives, occasionally, some filaments to the posterior part of the articulation. The last articular branch is the
posterior or azygos, which is given off opposite the joint, or from the inferior internal nerve : it perforates the posterior ligament, and is distributed to the articulation." We have observed this inferior articular nerve give off', occasionally, muscular filaments to the plan taris, and upper part of the poplitteus.
The cutaneous branch is named the tibial sa pheenus (external saphmnus —communicating saphmnus—communicans tibite), and takes its origin from the back part of the trunk ex ternal to the muscular branches. It inclines a little to the outside of the middle of the poplitmal space, under the fascia, but super ficial to the gastrocnemius, along the posterior surface of which it pa.sses till it perforates the fascia at a variable distance from the ankle, and receives the corresponding branch from the peronmal saphmnus. It is then directed, under the name of the external saphernus, along the outer part of the tendo Achillis to the outer and back part of the external ankle, where it divides into its terminal branches. In the first part of its course it lies to the inside of the external saphmna vein. Near the lower angle of the poplitmal span it passes in front of the vein to get to its outside, continues external to it as far as about an inch above the outer ankle, and again passes in front of it to its inside.
The tibial saphmnus gives off no branch till it becomes external saphmnus, and internal and external cutaneous branches arise from it. The internal supply the outer and back part of the leg: and a superior and inferior calcaneal branch are generally observed. The superior is directed over the tendo Achillis, supplies the skin at the inner and back part .of the heel, and communicates with filaments from the external plantar : the inferior passes along the outer border of the tendo Achillis to the skin at the outer and lower part of the heel. The outer cutaneous run downwards and forwards over the tendon of the pero nmus long,us, as far as the malleolus externus, communicating above with descending fila ments of the peronmal cutaneous ; and below with the malleolar filaments of the musculo cutaneous. Independent of these, cutaneous filaments and a few delicate nerves are given off, which accompany the saphtena vein.