The human foot and the human hand

by George Murray Humphry

Fig. [7].

One, the Plantar Ligament (A, fig. 7), of great strength, passes from the under surface of the heel-bone, near its extremity, forwards, to the ends of the metatarsal bones; in other words, it extends between the lowest points of the two pillars of the arch, girding, or holding, them in their places, and preventing their being thrust asunder when pressure is made upon the key-bone (D); just as the “tie-beam” of a roof resists the tendency to outward yielding of the sides when weight is laid upon the summit. The ligament, however, has an advantage which no tie-beam can ever possess; inasmuch as a quantity of muscular fibres are attached along the hinder part of its upper surface. These instantly respond to any demand that is made upon them, being thrown into contraction directly the foot touches the ground; and the force of their contraction is proportionate to the degree of pressure which is made upon the foot. Thus they add a living, self-acting, self-regulating power to the passive resistance of the ligament. In addition to its office of binding the bones in their places, the ligament serves the further purpose of protecting from pressure the tender structures—the blood-vessels, nerves and muscles—that lie above it, in the hollow of the foot, under the shelter of the plantar arch.

Another very strong ligament (B in the wood-cut) passes from the under and fore part of the heel-bone (F) to the under part of the scaphoid bone (E). It underlies and supports the round head of the astragalus, and has to bear a great deal of the weight which is transmitted to that bone from the leg. It does not derive the same assistance from a close connexion with muscular fibres as the ligament just described; but it possesses a quality, which that and most other ligaments do not have, viz. elasticity. This is very important, for it allows the head of the key-bone (D) to descend a little, when pressure is made upon it, and forces it up again when the pressure is removed, and so gives very material assistance to the other provisions for preventing jars and for giving ease and elasticity to the step.

A glance at the drawing will show you that here is a weak point in the foot. The head of the key-bone receives great weight from the leg, but is comparatively unsupported; and there is a considerable strain upon this part when the heel is being raised in walking. Moreover, a good deal of movement takes place between the key-bone (D) and the scaphoid bone (E), more than between any other two bones of the instep; and freedom in the range of movement is generally attended with some sacrifice of strength. The strong elastic ligament comes in therefore with peculiar advantage at this point; and it is underlaid, and additional support is afforded exactly when it is most required, by the tendon (b in fig. [12]) of a strong muscle, the especial office of which is to assist in raising the heel and bending the instep, and which runs, from the back of the leg, behind the inner ankle, to the scaphoid bone.

Weak Ankle and Flat-foot.

In spite, however, of the thick elastic ligament and the strong tendon just mentioned, the joint between the astragalus or key-bone and the scaphoid bone still remains a weak point. The head of the key-bone, from being insufficiently supported or from being overweighted, is very apt to descend a little below its proper level; the consequence of which is that the plantar arch is lowered and the foot is flattened; and the more the foot is flattened the weaker it necessarily is, because the position of the bones then becomes less and less favourable for bearing weight, and an increasing strain is thus incurred by the ligaments and muscles. Hence the foot and ankle feel weak; and the weakness is especially felt when the person endeavours to raise the heel, so as to mount upon the balls of the toes, in walking. For the performance of that movement with ease and steadiness a well-formed plantar arch is essential; and the person, whose feet are defective in the manner we are considering, can never walk with a bold, firm step. The movement in him may be better described as a shuffling from one foot on to the other, than as a walk. To this I will recur again when I come to speak more of walking. The defect, when slight in degree, is commonly called “weak-ankle;” when more decided it is called “flat-foot,” because the sole is then nearly, or quite, flat. The head of the key-bone, under such circumstances, may even bulge downwards and inwards, and form a prominence on the inner side of the sole, so as to give more or less convexity to the line on the inner side of the foot, which should be concave.

Fig. [8]. Flat-foot.

The representation of “flat-foot” here shown was drawn from the foot of a labouring man in this county. He said he believed the deformity was due to his having worn thick tight shoes when he was a growing boy. He is most likely right in his opinion; for tight or ill-fitting shoes, cramping the feet and preventing the proper growth of the bones and the free play of the muscles, are a common cause of this evil. This is so especially among the agricultural class, whose feet are, from an early period, enclosed in stiff unyielding leather cases that are enough to mar nature’s best efforts to construct a plantar arch.

The same drawing shows that flat-foot is not the only deformity for which “high-lows” are answerable. Besides the almost total want of calf, which is due to the wearer being obliged to hobble along, whole-footed, with short feeble steps, it will be seen that the great toe has not been allowed to assume its natural straight line, but has been squeezed athwart the other toes, so as to be almost at a right angle with the foot. No room at all is thus given for the second toe; it has been driven quite out of the field, and has been obliged to hide itself by bending down under the other toes. This is no uncommon state of things. Frequently it is attended with the formation of a painful bunion upon the prominent inner side of the ball of the great toe; and, in addition, there is sometimes a corn upon the first joint of the second toe, which is a source of so much inconvenience that I have known many sufferers glad to get relief by parting with the toe.