The Divine Institutes

In the beginning, when God was forming the animals, He did not wish to conglobate and collect them into a round shape, that they might be able easily to put themselves in motion for walking, and to turn themselves in any direction; but from the highest part of the body He lengthened out the head. He also carried out to a greater length some of the limbs, which are called feet, that, being fixed on the ground with alternate motions, they might lead forward the animal wherever his inclination had borne him, or the necessity of seeking food had called him. Moreover, He made four limbs standing out from the very vessel of the body: two behind, which are in all animals—the feet; also two close to the head and neck, which supply various uses to animals. For in cattle and wild beasts they are feet like the hinder ones; but in man they are hands, which are produced not for walking, but for acting and controlling. There is also a third class, in which those former limbs are neither feet nor hands; but wings, which, having feathers arranged in order, supply the use of flying. Thus one formation has different forms and uses; and that He might firmly hold together the density itself of the body, by binding together greater and small bones, He compacted a kind of keel, which we call the spine; and He did not think fit to form it of one continued bone, lest the animal should not have the power of walking and bending itself. From its middle part, as it were, He has extended in a different direction transverse and flat bones, by which, being slightly curved, and almost drawn together to themselves as into a circle, the inward organs may be covered, that those parts which needed to be soft and less strong might be protected by the encircling of a solid framework. But at the end of that joining together which we have said to resemble the keel of a ship, He placed the head, in which might be the government of the whole living creature; and this name was given to it, as indeed Varro writes to Cicero, because from this the senses and the nerves take their beginning.

But those parts, which we have said to be lengthened out from the body, either for the sake of walking, or of acting, or of flying, He would have to consist of bones, neither too long, for the sake of rapidity of motion, nor too short, for the sake of firmness, but of a few, and those large. For either they are two as in man, or four as in a quadruped. And these He did not make solid, lest in walking sluggishness and weight should retard; but He made them hollow, and full of marrow within, to preserve the vigour of the body. And again, He did not make them equally extended to the end; but He conglobated their extremities with coarse knots, that they might be able more easily to be bound with sinews, and to be turned more easily, from which they are called joints. These knots He made firmly solid, and covered with a soft kind of covering, which is called cartilage; for this purpose, that they might be bent without galling or any sense of pain. He did not, however, form these after one fashion. For He made some simple and round into an orb, in those joints at least in which it was befitting that the limbs should move in all directions, as in the shoulders, since it is necessary that the hands should move and be twisted about in any direction; but others He made broad, and equal, and round towards one part, and that plainly in those places where only it was necessary for the limbs to be bent, as in the knees, and in the elbows, and in the hands themselves. For as it was at the same time pleasant to the sight, and useful, that the hands should move in every direction from that position from which they spring; so assuredly, if this same thing should happen to the elbows, a motion of that kind would be at once superfluous and unbecoming. For then the hand, having lost the dignity which it now has, through its excessive flexibility, would appear like the trunk of an elephant; and man would be altogether snake-handed,—an instance of which has been wonderfully effected in that monstrous beast. For God, who wished to display His providence and power by a wonderful variety of many things, inasmuch as He had not extended the head of that animal to such a length that he might be able to touch the earth with his mouth, which would have been horrible and hideous, and because He had so armed the mouth itself with extended tusks, that even if he touched the earth the tusks would still deprive him of the power of feeding, He lengthened out between these from the top of the forehead a soft and flexible limb, by which he might be able to grasp and lay hold of anything, lest the prominent magnitude of the tusks, or the shortness of the neck, should interfere with the arrangement for taking food.