Timaeus

Moreover, we must trace out in this way the causes of the phenomena connected with medical cupping-glasses, and the causes of deglutition, and of projectiles, whether discharged aloft or flying over the surface of the earth; and the causes also of all the sounds which because of their quickness or slowness seem shrill or deep, and the movement of which is at one time discordant because of the irregularity of the motion they cause within us, and at another time concordant because of its regularity. For the slower sounds overtake the motions of the earlier and quicker sounds when the latter begin to stop and have already fallen to a speed similar to that with which the slower sounds collide with them afterwards and move them; and when the slower overtake the quicker sounds they do not perturb them by imposing upon them a different motion, but they attach to them the beginning of a slower motion in accord with that which was quicker but is tending to cease; and thus from shrill and deep they blend one single sensation, furnishing pleasure thereby to the unintelligent, and to the intelligent that intellectual delight which is caused by the imitation of the divine harmony manifested in mortal motions. Furthermore, as regards all flowings of waters, and fallings of thunderbolts, and the marvels concerning the attraction of electron and of the Heraclean stone—not one of all these ever possesses any real power of attraction; but the fact that there is no void, and that these bodies propel themselves round one into another, and that according as they separate or unite they all exchange places and proceed severally each to its own region,—it is by means of these complex and reciprocal processes that such marvels are wrought, as will be evident to him who investigates them properly. Moreover, the process of respiration—with which our account commenced—came about, as we previously stated, in this manner and by these means. The fire divides the foods, and rises through the body following after the breath; and as it rises, with the breath it fills the veins from the belly by drawing into them from thence the divided particles. And it is owing to this that in all living creatures the streams of nutriment course in this way through the whole body. And inasmuch as these nutritive particles are freshly divided and derived from kindred substances,—some from fruits, and some from cereals, which God planted for us for the express purpose of serving as food,—they get all varieties of colors because of their commingling, but red is the color that runs through them most of all, it being a natural product of the action of the fire in dividing the liquid food and imprinting itself thereon.