Figs. 77 to 81.
Contact of the sole with the ground in normal walking. Heel first then toe, with progressive dorsiflexion of the ankle joint. Compare with the contact of the artificial foot in [figures 82 to 86].
With boots on, with heels of 2·5 centimetres the two feet are in the same position when the soles are flat on the ground.
The forepart of the foot (representing the toes and the anterior part of the metatarsals) is kept in this position ([Fig. 76]) in slight extension by a piece of rubber, compression of which allows an increase of extension of 15° to 20°.
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).
Figs. 82 to 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.