Timaeus — Plato

never at any time ceasing so long as the mortal being holds together. This process, as we affirm, the name-giver named inspiration and expiration.

And all this movement, active as well as passive, takes place in order that the body, being watered and cooled, may receive nourishment and life ; for when the respiration is going in and out, and the fire, which is fast bound within, follows it, and ever and anon moving to 79 and fro, enters through the belly and reaches the meat and drink, it dissolves them, and dividing them into small portions and guiding them through the passages where it goes, pumps them as from a fountain into the channels of the veins, and makes the stream of the veins flow through the body as through a conduit.

Let us once more consider the phenomena of respiration, and enquire into the causes which have made it what it is.

They are as follows: — Seeing that there is no such thing as a vacuum into which any of those things which are moved can enter, and the breath is carried from us into the external air, the next point is, as will be clear to every one, that it does not go into a vacant space, but pushes its neighbour out of its place, and that which is thrust out in turn drives out its neighbour ; and in this way everything of necessity at last comes round to that place from whence the breath came forth, and enters in there, and following the breath, fills up the vacant space ; and this goes on like the rotation of a wheel, because there can be no such thing as a vacuum.

Wherefore also the breast and the lungs, when they emit the breath, are replenished by the air which surrounds the body and which enters in through the pores of the flesh and is driven round in a circle ; and again, the air which is sent away and passes out through the body forces the breath inwards through the passage of the mouth and the nostrils. Now the origin of this movement may be supposed to be as follows.

In the interior of every animal the hottest part is that which is around the blood and veins ; it is in a manner an internal fountain of fire, which we compare to the network of a creel, being woven all of fire and extended through the centre of the body, while the outer parts are composed of air. Now we must admit that heat naturally proceeds outward to its own place and to its kindred

Tunaeus. TiMAEUS. following the air in either direction. The motion of the fire into and out of the belly dissolves the food and pumps the blood into the veins.

Expiration and inspiration take place through the pores as well as through the mouth and nostrils. Expiration is due to the attraction of similars: the air on entering the body is heated, and then moves outward, seeking the place of fire. Inspiration is due to the impossibility of a vacuum ; thus while air is breathed out of the body, other air must enter to fill the vacancy.

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The harmony of sounds.

Tijitaeus. TiMAEUS.

Other phenomena to be explained on a similar principle: — Cuppingglasses, swallowing of drink, projection of bodies, sounds swift and slow, flowing of water, fall of thunderbolts, magnetic stones.

element ; and as there are two exits for the heat, the one out through the body, and the other through the mouth and nostrils, when it moves towards the one, it drives round the air at the other, and that which is driven round falls into the fire and becomes warm, and that which goes forth is cooled.

But when the heat changes its place, and the particles at the other exit grow warmer, the hotter air inclining in that direction and carried towards its native element, fire, pushes round the air at the other; and this being affected in the same way and communicating the same impulse, a circular motion swaying to and fro is produced by the double process, which we call inspiration and expiration.

The phenomena of medical cupping-glasses and of the swallowing of drink and of the projection of bodies, whether 80 discharged in the air or bowled along the ground, are to be investigated on a similar principle ; and swift and slow sounds, which appear to be high and low, and are sometimes discordant on account of their inequality, and then again harmonical on account of the equality of the motion which they excite in us.

For when the motions of the antecedent swifter sounds begin to pause and the two are equalized, the slower sounds overtake the swifter and then propel them.

When they overtake them they do not intrude a new and discordant motion, but introduce the beginnings of a slower, which answers to the swifter as it dies away, thus producing a single mixed expression out of high and low, whence arises a pleasure which even the unwise feel, and which to the wise becomes a higher sort of delight, being an imitation of divine harmony in mortal motions.

Moreover, as to the flowing of water, the fall of the thunderbolt, and the marvels that are observed about the attraction of amber and the Heraclean stones, — in none of these cases is there any attraction ; but he who investigates rightly, will find that such wonderful phenomena are attributable to the combination of certain conditions, — the non-existence of a vacuum, the fact that objects push one another round, and that they change places, passing severally into their proper positions as they are divided or combined. Such, as we have seen, is the nature and such are the causes of respiration, — the subject in which this discussion