The Skin of the Sole
The Skin of the sole is soft and yet very tough and strong. It underlies a thick pad of fat, which separates it from the bones and the plantar ligament. The fat is interwoven with fibres passing, through it, from the tissue of the skin to the bones and ligaments. It is, in this way, rendered very firm, though it retains much of the soft quality of fat; and it forms an admirable cushion for receiving the weight of the body and defending from injurious pressure both the skin and the other parts of the foot. The fibres just mentioned bind the skin to the superjacent bones and ligaments, and hold it firmly to them, so as to prevent its being displaced from them in the movements of the foot upon the ground.
The accompanying woodcut shows that these connecting fibres are most numerous where there is the greatest pressure, viz. beneath the heel and the balls of the toes. It shows, too, that they take the direction at each of those parts which is most calculated to prevent displacement. Thus, at the heel their direction is chiefly from the heel-bone, backwards, to the skin. When we place the heel upon the ground in walking, the weight of the body has a tendency to drive the heel-bone forwards from the skin; and the direction of the fibres, from the heel-bone, backwards, just resists this tendency and holds the skin and the bone firmly together. On the contrary, when we withdraw the foot from the ground the pressure is in the opposite direction, and has a tendency to drive the metatarsal bones backwards from the skin. The course of the fibres is, consequently, changed. They, many of them at least, run forwards from the bones and prevent the displacement that would be likely to occur. This direction is also very marked, and for the same reason, at the end of the great toe. A bundle of fibres radiates from the projecting process, or tubercle, which is conspicuous upon the under surface of the bone near its end; and the greater number of them run forwards, through the pulp of the toe, to the skin, and maintain the connection of the skin with the bone when the latter is pressed backwards in withdrawing the foot from the ground.
The skin of the sole has a peculiar sensitiveness, which enables it to take quick cognisance of contact with the ground or of any injurious substances lying upon the ground. The sensitiveness in the foot is rather increased by its being so much covered up. We are aroused to a consciousness of this sensitiveness when the soles are tickled, or when any one treads on our toes, especially if there happen to be a corn there. We know also how sensitive the feet are to cold, and how liable we are to catch cold from wet feet. This sensitiveness renders washing the feet a refreshing luxury, especially in hot climates or when we are fatigued. It is a luxury much indulged in by Eastern nations; “Mephibosheth had neither dressed his feet nor trimmed his beard from the day the king departed, until he came again in peace;” and among the Jews in our Saviour’s time (Luke vii. 38), when guests were made very welcome, their sandals were unloosed, and their feet washed and carefully wiped, and, if the person were of high rank, anointed.
The integument of the foot varies in different animals, according to the nature of the ground upon which they tread and other circumstances. Thus the Elephant, the Hippopotamus, and the Rhinoceros, living in jungles and in marshy districts, have a more or less soft covering of skin. Oxen and Horses gallop about upon dry ground; and their feet are soled with thick hoofs of horn. The Dog has tough pads of skin with thick cuticle upon his feet; and the feet of the Feline tribe are muffled with fur so as to enable them to approach their prey with a noiseless tread. Man’s foot is, by nature, like the rest of the surface of his body, comparatively unprotected; but as the foot, by its efficiency, emancipates the hand from the drudgery of carrying, so does the latter make some return for this relief by providing artificial coverings which enable the foot to tread upon various surfaces, and protect it against the inclemencies of the seasons.