Its The lower portion is the more important of the two. attachments have already been noted (p. 259). Examine the manner in which it holds the tendons in their place. It consists of two layers, and these, by separating at certain points and becoming re-united at others, form three distinct compartments. Through the innermost passes the tendon of the tibialis anticus; through the middle one passes the tendon of the extensor longus hallucis; and through the outermost are transmitted the tendons of the extensor longus digitorum and peroneus tertius. On opening up these sheaths each will be seen to be lined by a synovial membrane. Lastly, note the position of the anterior tibial vessels and nerve as they pass under cover of the ligament. They lie between the extensor longus hallucis and the extensor longus digit orum. PERONEAL REGION The peroneal or outer compartment of the leg should now be opened by dividing, in a longitudinal direction, the fascia which covers it. Enclosed within it are : 1. The peroneus longus. 2. The peroneus brevis. 3. The termination of the external popliteal nerve. 4. The musculo-cutaneous nerve. The Peroneus Longus arises from the head and from the outer surface of the shaft of the fibula in its upper twothirds. A surface of origin is also afforded to it by the fascia which covers it, and by the two peroneal intermuscular septa. It ends a short distance above the ankle in a long tendon, which is continued downwards behind the external malleolus. Gaining the outer margin of the foot, it proceeds forwards to the groove on the under surface of the cuboid, which conducts it transversely into the sole. Its insertion will be examined at a later period. The Peroneus Brevis arises from the lower two-thirds of the outer surface of the shaft of the fibula, below and in front of the peroneous longus, and from the peroneal intermuscular septum on either side of it. Its tendon descends behind the external malleolus, and then turns forwards on the outer surface of the os calcis to gain an insertion into the projecting base of the metatarsal bone of the little toe.1 On the back of the external malleolus the tendon of the peroneus brevis lies directly under cover of the tendon of the peroneus longus, and therefore in contact with the bone. On the outer surface of the os calcis the tendon of the peroneus brevis is placed at a higher level than that of its fellow muscle. As the tendons of the two peronei muscles proceed downwards in the hollow between the external malleolus and the posterior prominence of the os calcis they are held in place by the external annular ligament, and their movements are facilitated by the presence of a common synovial sheath. On the outer surface of the os calcis each tendon is retained in position by a separate fibrous sheath, into which the common synovial membrane is prolonged. The peroneal tubercle of the os calcis intervenes between these two sheaths. External Popliteal Nerve (nervus peroneus communis) This nerve has previously been traced as far as the neck of the fibula. At this point it disappears from view by passing forwards between the peroneus longus muscle and the bone. The muscle must therefore be carefully turned aside from its origin in order that the nerve may be followed out. It will be found to give off a small recurrent articular nerve to the knee-joint, and then to divide into the anterior tibial and musculo-cutaneous nerves. The recurrent branch accompanies the anterior recurrent tibial artery. It turns upwards in the fibres of the tibialis 1 A small tendinous slip will, as a general rule, be observed to proceed forwards from the tendon of the peroneus brevis to join the tendon of the long extensor on the dorsum of the little toe. This is the peroneus quinti digiti. anticus. To the upper part of this muscle it gives several twigs, whilst its terminal filaments gain the front of the knee-joint. The anterior tibial nerve pierces the upper part of the extensor longus digitorum to reach the front of the leg, where it has already been dissected. The Musculo-cutaneous Nerve (nervus peronæus superficialis) proceeds downwards in the substance of the peroneus longus. It reaches the interval between the two peronei muscles, gives branches to both, and lastly comes to lie between the peroneus brevis and the extensor longus digitorum. In the lower third of the leg it pierces the fascia, and becomes cutaneous. TIBIAL REGION. This region corresponds to the subcutaneous or inner surface of the tibia. The deep fascia blends with the periosteum of the bone, and the only structures which have to be examined are: I. The internal saphenous vein. 3. The expanded tendons of insertion of the sartorius, semitendinosus, and gracilis. 4. Internal lateral ligament of the knee-joint. 5. Inferior internal articular artery and nerve. The internal saphenous nerve and vein, as they pass from the anterior to the posterior tibio-fibular region, cross obliquely over the lower third of the inner surface of the tibia. The insertion of the sartorius, gracilis, and semitendinosus into the upper part of the inner surface of the tibia should again be examined. Observe how the sartorius overlaps the tendons of the other two, and how the tendon of the gracilis overlaps the upper part of the tendon of the semitendinosus. A synovial bursa separates these tendons from each other. VOL. I.-18 The internal lateral ligament of the knee-joint will be seen extending downwards for a short distance upon the inner aspect of the shaft of the tibia. Passing forwards under cover of this ligament, so as to gain the anterior aspect of the knee, are the inferior internal articular vessels and nerve. POSTERIOR TIBIO-FIBULAR REGION. The following is a list of the structures which are met with in this dissection :— Reflection of Skin.-The limb must now be placed on its anterior aspect, and the muscles of the calf rendered tense by flexing the foot at the ankle-joint. This position should be maintained by the aid of hooks, fastened to the toes and to the under surface of the table. Incisions.—(1) A longitudinal incision along the middle line of the leg on its posterior aspect to the extremity of the heel. (2) A transverse incision at the lower end of this, extending along the inner and outer margins of the foot for about two inches on either side. The two flaps of skin thus marked out must be raised and turned outwards and inwards. Superficial Veins.-The internal and external saphenous veins must be traced in the substance of the fatty superficial fascia. Both of these vessels have been seen in previous steps of the dissection. The internal saphenous vein has been observed to arise from the inner extremity of the venous arch on the dorsum of the foot, and it has been followed upwards for a short distance in front of the inner malleolus, and then upon the inner aspect of the lower part of the tibia. It has also been dissected upon the inner aspect of the thigh and knee. It can now be exposed in its course along the inner side of the calf of the leg. It lies a short distance behind the internal border of the tibia. The external saphenous vein has been seen to arise from the outer end of the dorsal arch and to pass upwards behind the outer malleolus. It may now be followed as it ascends along the outer side of the tendo Achillis to the back of the leg, where it lies over the interval between the two heads of the gastrocnemius muscle. When it gains the lower part of the popliteal space it pierces the deep fascia and joins the popliteal vein. Associated with each of these veins are certain cutaneous nerves, which must be displayed at the same time. The small sciatic is closely related to the external saphenous vein in its upper part, and the external saphenous nerve accompanies it in the lower half of the leg. In company with the internal saphenous vein we find the internal or long saphenous nerve. Cutaneous Nerves.-These are very numerous. On the inner side of the leg are (1) the internal or long saphenous; (2) the posterior branch of the internal cutaneous; and (3) the internal calcanean. The guide to the internal saphenous nerve is the vein of the same name. It may now be exposed in its entire course along the inner side of the leg. The posterior branch of the internal cutaneous proceeds downwards a short distance behind the preceding nerve. It usually ends about the middle of the leg. The internal calcanean is a branch of the posterior tibial nerve. Dissect for it in the interval between the prominence of the heel and internal malleolus. It pierces the internal annular ligament nearer the former |