This section is from the book "The Manufacture Of Boots And Shoes: Being A Modern Treatise Of All The Processes Of Making And Manufacturing Footgear", by F. Y. Golding. Also available from Amazon: The Manufacture Of Boots And Shoes.
The bones of the foot form two arches, one longitudinal and the other transverse. The longitudinal arch extends from the os calcis behind to the heads of the metatarsal bones in the front, being situated in the long axis of the foot. Its height and span are greatest on the inner side, and the distance from the ground lessens towards the outside of the foot (Fig. 9). The impression made by standing on a flat surface with wet feet will show how much flatter the outside margin is than the inside. The arch is mainly supported by the calcaneo-cuboid ligament. It is complete in each foot, and the posterior pier or pillar formed by the heel-bone descends almost straight to the ground, whereas the an-terior pillar slopes gradually to the ball of the foot (Fig. 12). The arch is therefore solid behind and elastic or springy in front.
The transverse arch (Fig. 11) extends from side to side, and is most marked over the instep - that is, its convexity is across the cuneiform and cuboid bones. It forms half a dome in each foot, with its greatest height on the inner side. Flat foot, or the bearing down of the arches, is most likely to be engendered - first, in infancy, if the child be put upon its feet too early, before the ligaments and bones are sufficiently developed to bear the weight of the body; and,secondly, about the age of fourteen, when the body attains a greater increase of weight. From what has been said respecting the ligaments, it will be seen that binding up the ankle in stiff leather coverings, or the making of stiff shanks to shoes, are not the methods best calculated to restore the arch of the foot. It will be well here to consider some of the effects of the falling arch as it affects foot-gear. When the arch lowers, the os calcis is pushed backwards, making the foot long heeled; at the same time the astragalus advances towards the front, and adds to the foot's length. The leg thus has the appearance of being pitched more towards the middle of the foot. In a foot that is well arched, the projection of bone at the upper part of the heel-bone extends further back than the lower edge, and in a flatter foot the bottom part of the heel-bone extends further back than the upper. When weight is transmitted to the foot, the arches expand both longitudinally and transversely. The expansion of the long arch of the foot is greatest in high-arched, long, slender feet, and least in low-arched, short, strong, thick feet. The expansion laterally is greatest in high-arched broad feet, and least in low-arched narrow ones.
Fig.11. Section Of Transverse Arche.
The Muscles supply the motive power by which the various motions of the leg and foot are performed. A muscle consists of red fleshy masses of fibre possessing contractile properties. It is soft and thick in the middle, and at each end tapers to a point, changing into a band by which it is fastened to the bones. It is a very active living substance, that is capable of shortening in one direction and thickening in another, under nervous action or stimuli. It does not alter in actual bulk, but only changes its direction. Muscle consists of bundles of fibres intermixed with nerves and blood-vessels. They are variously shaped, according to office, and are mostly attached to bones, which when movable are brought together. The smaller extremities of a muscle that end in a tendon are termed origin and insertion, as they are fixed either to stationary or movable bone respectively. Locomotion is accomplished by various combined actions of many distinct muscles, placed together in the limbs.
The Naming of Muscles is usually from their shape, function, or position. Those we have to deal with are classed Abductors - muscles that draw from. Adductors - „ draw to.
Flexors - „ bend limbs.
Extensors - „ straighten limbs.