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the ground, and really to throw nearly the whole force in that direction. Moreover, you may observe that when we walk, the weight of the body is partly sustained by the fore part of the one foot till the whole of the other foot is on the ground. I will, however, revert to the disposition of the feet in walking and running presently.

The arch of the foot has to bear great weight and at great disadvantage; and there is very little in the shape of the bones to maintain its integrity. Indeed, they all fall asunder when the other structures are removed, the key-bone dropping through of its own weight. And the same thing may be remarked throughout the skeleton. Wherever two or more bones move upon one another, their surfaces are so constructed that they do not hold together without some assistance from the soft parts. There are joints in the body which we call "hinge-joints," and others which we call "ball-and-socket joints;" but in none of them is there such a holding and locking of one part in the other as you have in the hinge and the ball-and-socket of the mechanic. In every case the bones are held together, not by their own shape, but by ligaments and muscles. Consequently, any one of the bones may be dislocated from those next it without breakage; and when the muscles and ligaments are cut

through, or have been destroyed by maceration, all the bones, between which any movement was possible during life, separate from one another.

Not only is this so, but in no instance are the movements of joints limited simply by the shape of the bones-that is to say, they are never brought to a stop by a part of one bone coming into contact with the edge of another. Such a contact would have caused a sudden check; and this would have been attended with more or less jar and with some danger of chipping and breaking the articular edges. The range of movement of a joint is always regulated by the ligaments or the muscles, not, directly, by the bones; and the restraint thus imposed upon the movements is brought to bear, not suddenly, but gradually; somewhat like the effect of the "break" upon a railway-train; while the cartilages between the bones may be compared with the "buffers" between the carriages.

It is chiefly by means of strong LIGAMENTS, or sinewy bands, passing from bone to bone, that the shape of the plantar arch is maintained and the movements of the bones upon one another are regulated and limited. These ligaments are numerous; but I will mention only two.

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 keybone (D); just as the "tie-beam" of a roof resists

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the tendency to outward yielding of the sides when weight is laid upon the summit. The ligament, however, has an advantage which no tiebeam 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 bloodvessels, 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 woodcut) 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

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