The human foot and the human hand

by George Murray Humphry

The drawing represents a section, from behind forwards, of the lower end of the leg-bone, and of the bones lying along the inner side of the plantar arch. Behind it extends through the heel-bone, and in front through the great toe. It exhibits the arrangement of the fibres and plates in the interior of the bones, and shows that the greater number of them, in each bone, follow the direction of the two pillars of the arch; that is to say, they descend from the summit of the arch where it supports the leg-bone, backwards and downwards, to the heel, and, forwards and downwards, to the balls of the toes. Their arrangement is, therefore, such as to give resisting strength to the bones in the directions in which it is most required.

You may think that the arch of the foot would have been a much simpler structure, as well as stronger, if it had been composed of one bone instead of several. But it must be remembered that it would, then, have been liable to be cracked and broken by the sudden and violent manner in which, during running and jumping, the weight of the body is thrown upon it. Moreover, the several bones, where they touch one another, are covered with a tolerably thick layer of highly elastic gristle or cartilage (represented by the clear line left in the drawing along the contiguous edges of the bones); and this provision, together with the slight movements which take place between these bones, gives an elasticity to the foot and to the step, and serves to break the jars and shocks which are caused by the sudden contact of the foot with the ground.

This last is a very important point; and we find numerous contrivances in different parts of the body to protect the brain and other delicate organs from jars. So efficient are these contrivances, and so exact is the adaptation of the mechanism of the limbs and the trunk to the texture of the internal organs, that, while these are in a healthy state, we are able to run, to jump, and to leap from a considerable height, without inconvenience. But, if the organs be inflamed, or if the nervous system be over sensitive, as in common headache, the provisions, which are calculated for the normal state, are insufficient; ordinary movements are then painful, and to jump is intolerable.

The muscles play a very essential part in this work. First, they place the limbs in the most favourable position. Thus, when we alight upon the ground, from a height, we always contrive to do so with the knees and hips a little bent, so that the limbs readily yield at the joints, and act as springs to break the jar. Elderly persons commonly keep the limbs bent, even when walking quietly along. They do this because they need all the benefit which position will afford to make amends for the loss of elasticity consequent on the thinning and drying of the cartilages, and other changes that take place in the body with advancing years. Secondly, the muscles brace the limbs and joints in the position in which they have placed them. We experience the effect of the want of this salutary influence when we kick against an unseen object, or fall suddenly, or receive any blow or shock for which we are unprepared. How disagreeable, to say the least, it is to make the step for an additional stair when we have arrived at the top of a staircase, or, still worse, to meet with an unseen stair when we think that we have got to the bottom.

You perceive from the drawing (fig. [6]) that there is a great difference between the two pillars of the plantar arch. The hinder pillar is comparatively short, and narrow, and descends suddenly, almost in a vertical direction, from the ankle, to the ground; and it is composed of only one bone—the heel-bone—which is jointed directly with the astragalus: whereas the fore pillar is longer and broader, is composed of several bones jointed together, and slopes much more gradually to the ground. There is, therefore, far less elasticity in the hinder part of the foot than in the fore part. Hence, when we descend from a height upon the ground, we always alight upon the balls of the toes, and thus gain the advantage which the several bones and joints afford in breaking the shock. If, after going up stairs this evening, you take the trouble to come down again, you will find that you alight upon each stair on the balls of the toes and experience no inconvenience, however quickly the descent is made. But, if you change the mode of proceeding, and descend upon the heels, the feeling will be by no means agreeable; and the various organs of the body, being disturbed from their accustomed repose, will raise such remonstrances against your infringement upon nature’s ways, that you will scarcely be able to continue the experiment. Proportionately more distressing is the sensation caused by jumping from a chair upon the heels. Indeed, this is not done altogether without risk; and the trial of it is scarcely to be recommended to persons who have attained to that sober period of life at which we are willing to concede that, in some things, nature is wiser than ourselves. Only a short time since I saw a gentleman, who, in jumping down some steps into a back yard, accidentally came upon his heels, and jarred one hip so severely that he was confined to his sofa for several days in consequence.

But, you may say, “in walking we do place the heel upon the ground first and experience no inconvenience.” True, because the force with which the foot descends in walking is very slight; and the weight is directed upon the heel, obliquely, in such a manner as to bring the toes very quickly to 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.