The phenomena of medical cupping-glasses and of the swallowing of
drink and of the projection of bodies, whether 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 originated. For
the fire cuts the food and following the breath surges up within,
fire and breath rising together and filling the veins by drawing
up out of the belly and pouring into them the cut portions of the
food; and so the streams of food are kept flowing through the
whole body in all animals. And fresh cuttings from kindred
substances, whether the fruits of the earth or herb of the field,
which God planted to be our daily food, acquire all sorts of
colours by their inter-mixture; but red is the most pervading of
them, being created by the cutting action of fire and by the
impression which it makes on a moist substance; and hence the
liquid which circulates in the body has a colour such as we have
described. The liquid itself we call blood, which nourishes the
flesh and the whole body, whence all parts are watered and empty
places filled.