malleolus the inner edge of the sustentaculum tali may be recognised, and about one inch or a little more in front of this we recognise the tubercle of the scaphoid. Then comes the internal cuneiform bone, and this is succeeded by the first metatarsal bone. None of these bony points can be said to form distinct prominences on the surface of a well-developed foot. In order to distinguish them the inner margin of the foot must be judiciously manipulated by the fingers. On the outer margin of the foot the tubercle on the base of the fifth metatarsal bone stands out as a distinct landmark. Behind this is the cuboid, and still further back the outer surface of the os calcis, which is almost completely subcutaneous. When present in a welldeveloped form the peroneal tubercle on this surface may be distinguished about one inch below and a little in front of the external malleolus. If the foot be strongly inverted the anterior end of the os calcis will be seen to project on the surface.

Subdivision of the Leg into Regions. In the dissection of the leg four distinct regions may be recognised, viz. :

1. An anterior tibio-fibular region, in which are placed those structures which lie in front of the interosseous membrane, and between the two bones of the leg.

2. A tibial region, corresponding to the subcutaneous or inner surface of the shaft of the tibia.

3. A peroneal region, which includes the parts in relation to the outer surface of the fibula.

4. A posterior tibio-fibular region, in which are placed the parts on the back of the leg which lie behind the interosseous membrane and the two bones of the leg.

ANTERIOR TIBIO-FIBULAR REGION-DORSUM OF FOOT.

The anterior tibio-fibular region should be dissected first, and it is usual to conjoin with this the dissection of the dorsum of the foot. The following parts are exposed in this region:

Reflection of Skin.-To place the limb in a convenient position for the dissection of this region, a block should be introduced beneath the knee, and the foot should be extended and fastened firmly to the table by means of hooks. The skin should be reflected from the tibial and peroneal regions at the same time. Incisions:-(1) a vertical cut along the middle line of the leg and dorsum of the foot to the base of the middle toe; (2) a transverse incision across the ankle-joint; (3) a transverse incision across the dorsum of the foot at the roots of the toes.

The four flaps of skin thus mapped out must now be raised from the subjacent fatty tissue, and the superficial veins and nerves dissected

out.

Superficial Veins.-The venous arch on the dorsum of the foot, which receives the digital veins, should in the first place be dissected. From the inner extremity of this arch the internal saphenous vein will be seen to take origin, whilst from its outer end the external saphenous vein proceeds. Trace these vessels upwards. The former will be found to pass in front of the internal malleolus, whilst the latter ascends behind the external malleolus. Each is associated with the nerve which bears its own name. Cutaneous Nerves.-The following are the cutaneous nerves which must be secured in this dissection:

1. A branch from the external popliteal.

2. External saphenous.

3. Internal saphenous.
4. Musculo-cutaneous.
5. Anterior tibial.

:

The branch from the external popliteal frequently arises in common with the ramus communicans fibularis. It turns forwards, and is distributed upon the outer and anterior aspect of the leg in its upper part. The external

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saphenous nerve can be readily found. It reaches the outer margin of the foot by passing behind the external malleolus in company with the vein of the same name. Trace it forwards, and it will be found to end upon the fibular side of the little toe. On the dorsum of the foot a connecting twig passes between the external saphenous and the outer division of the musculo-cutaneous nerve. The internal or long saphenous nerve should be looked for in front of the inner malleolus. It descends in company with the internal saphenous vein. It can with care be followed half-way along the inner margin of the foot, but there it ends. Above the ankle-joint several minute twigs from this nerve may be found passing forwards to reach the front of the leg.

The cutaneous portion of the musculo-cutaneous nerve appears in the lower third of the leg. It pierces the deep fascia a short way to the outside of the middle line of the limb. Almost immediately it splits into an inner and an outer part. The inner division extends forwards on the dorsum of the foot, and sends one branch to the inner side of the great toe, and a second to supply the adjacent sides of the second and third toes. It likewise gives a number of twigs to the skin upon the inner margin of the foot, and effects a junction with the anterior tibial and internal saphenous nerves. The outer division is smaller than the inner part. It gives several twigs to the skin on the dorsum of the foot, communicates with the external saphenous nerve, and then divides into two branches, which supply the contiguous margins of the third, fourth, and fifth toes. Therefore, with the exception of the adjacent sides of the great toe and the second toe, which are supplied by the anterior tibial nerve, and the outer side of the little toe, which is supplied by the external saphenous nerve, the musculo-cutaneous nerve furnishes twigs to the two margins of each of the toes.1

1 Very frequently the distribution of the musculo-cutaneous nerve is more restricted, and in these cases the external saphenous nerve will, in all probability, be found to supply the outer two and a half toes.

The anterior tibial nerve, or rather its internal terminal branch, pierces the deep fascia on the dorsum of the foot in the interval between the first and second metatarsal bones. It receives a communicating branch from the inner part of the musculo-cutaneous, and ends by dividing into two twigs, which go to supply the adjacent margins of the great toe and the second toe.

Deep Fascia. The fatty superficial fascia should be removed in order that the deep fascia may be displayed. This aponeurosis does not form a complete investment for the leg. It is absent over the internal subcutaneous surface of the tibia, and is attached to the anterior and internal borders of that bone. It is also absent over the triangular subcutaneous surface on the lower part of the fibula, being attached to the ridges which limit this area in front and behind. It is not equally dense throughout. In the upper part of the front of the leg it is thick and strong, but it thins as it is traced downwards, and on the dorsum of the foot it becomes exceedingly fine. Its great strength in the upper part of the front of the leg is due to the fact that here it gives origin to subjacent muscles. In the neighbourhood of the ankle-joint it forms the thickened. bands or annular ligaments which retain the tendons in position during the action of the muscles. Two of these may be examined at this stage, viz., the anterior and the external annular ligaments.

The anterior annular ligament consists of two portions— an upper and a lower. The upper part is a strong, broad band which stretches across the front of the leg immediately above the ankle-joint. By one extremity it is attached, to the fibula, and by the other to the tibia. The lower part is placed over the ankle-joint. Externally it presents the appearance of a narrow, well-defined band, which is fixed firmly to the anterior part of the os calcis. As this is traced inwards it will be observed to divide into two diverging limbs. Of these the upper is attached to the inner malleolus, whilst the lower passes to the inner margin of the foot, and becomes connected with the

plantar fascia. The different parts of the anterior annular ligament are continuous with the deep fascia, but can readily be distinguished on account of their greater density and thickness.

The external annular ligament is short and narrow, and

FIG. 54.-Diagrammatic representation of the fascia of the leg. The fascia of the tibialis posticus is more a muscular aponeurosis than a true fascial septum ; but it is convenient for descriptive purposes to regard it as one of the partitions.

bridges over the hollow between the external malleolus and the posterior prominence of the os calcis.

Intermuscular Septa.-As the deep fascia of the leg passes backwards over the fibular region, two strong intermuscular septa are given off from its deep surface. These are distinguished as the anterior and posterior peroneal septa. The anterior peroneal septum intervenes between the peroneal muscles and the extensor muscles, and is attached to the anterior border of the fibula. The posterior peroneal septum is interposed between the peroneal muscles. and the muscles on the back of the leg, and is attached to the external border of the fibula. The leg is thus subdivided into three osteo-fascial compartments, corre