When a step is taken, the heel of the foot first meets the ground, the leg pointing downwards and forwards. Then the whole sole comes to lie flat on the ground, the degree of equinus being increased, the posterior rubber compressed and the anterior relaxed (Figs. 82 and 83), but when the limb is vertical the sole still being flat on the ground, compression of the posterior diminishes and that on the anterior increases (Fig. 84). This remains unchanged up to the moment when the foot leaves the ground, whilst the heel rises and the weight is borne on the toe piece of the foot, which is forced into extension (Figs. 85 and 86). [Illustration: FIG. 82. FIG. 83. FIG. 84. FIG. 85. FIG. 86.] This method of using rubber cylinders is the simplest. Another method, good but more delicate, is shown in figures 87 and 88. In the leg below the calf are two cross pieces of wood; the lower placed transversely supports the upper which is antero-posterior and so increases its resistance to the cords which are attached to it. The shape of these pieces of wood can be seen in the figures and require no further explanation. The bolt of the ankle joint is the same as in the foot last described. To the antero-posterior cross piece are attached two cords, which pass through the foot and are attached beneath it, one under the heel, and the other about the level of the midtarsal joint. The posterior cord is inelastic and stops dorsiflexion of the foot. The anterior has a section of elastic in it; it prevents the dropping of the foot whilst the limb is being swung. A small pad of rubber placed in front beneath the anterior part of the leg piece allows, by its compression, the partial correction of the equinus when the sole is pressed flat on the ground. [Illustration: FIG. 87.] [Illustration: FIG. 88.] Some appliances allow the foot a little _lateral mobility_, by rotation around an antero-posterior axis, so that it may adapt itself to irregularities of the ground. We here illustrate the "Duplex foot," which is very ingenious but which has the defect that after a time the mechanism grates. The ankle attachment is carried out in the same way as in the limbs last described (in this particular limb it is attached by cords), but the foot piece is divided as in a sub-astragaloid amputation; the lower surface of the astragaloid piece bears a median antero-posterior projection, tapering posteriorly and enlarged into a knob anteriorly, this lies in a corresponding groove in the heel piece; alongside this are two rubber cushions which are alternately compressed and relaxed as the foot inclines to one or other side. [Illustration: FIG. 89.--Duplex Foot.] _Combined mechanism for knee and ankle joints._