Timaeus

This, then, He used, and fashioned thereof, by turning, a bony sphere round about the brain; and therein he left a narrow opening; and around the marrow of both neck and back He molded vertebrae of bone, and set them, like pivots, in a vertical row, throughout all the trunk, beginning from the head. And thus for preserving the whole seed He closed it in with a ring-fence of stony substance; and therein He made joints, using as an aid the power of the Other as an intermediary between them, for the sake of movement and bending. And inasmuch as He deemed that the texture of the bony substance was too hard and inflexible, and that if it were fired and cooled again it would decay and speedily destroy the seed within it, for these reasons He contrived the species known as sinew and flesh. He designed to bind all the limbs together by means of the former, which tightens and relaxes itself around the pivots, and thus cause the body to bend and stretch itself. And the flesh He designed to be a shield against the heat and a shelter against the cold; and, moreover, that in case of falls it should yield to the body softly and gently, like padded garments; and, inasmuch as it contains within it warm moisture, that it should supply in summer, by its perspiration and dampness, a congenial coolness over the exterior of the whole body, and contrariwise in winter defend the body sufficiently, by means of its fire, from the frost which attacks and surrounds it from without. Wherefore, with this intent, our Modeller mixed and blended together water and fire and earth, and compounding a ferment of acid and salt mixed it in therewith, and thus molded flesh full of sap and soft. And the substance of the sinews He compounded of a mixture of bone and unfermented flesh, forming a single substance blended of both and intermediate in quality, and he used yellow also for its coloring. Hence it is that the sinews have acquired a quality that is firmer and more rigid than flesh, but softer and more elastic than bone. With these, then, God enclosed the bones and marrow, first binding them one to another with the sinews, and then shrouding them all over with flesh. All the bones, then, that possessed most soul He enclosed in least flesh, but the bones which contained least soul with most and most dense flesh; moreover, at the junctions of the bones, except where reason revealed some necessity for its existence, He made but little flesh to grow, lest by hindering the flexions it should make the bodies unwieldy, because stiff in movement, or else through its size and density, when thickly massed together, it should produce insensitiveness, owing to its rigidity, and thereby cause the intellectual parts to be more forgetful and more obtuse.