The Timaeus of Plato

8o A] TIMAIO2. 299
is
heated, but that which passes out is cooled. So the heat
changes its position and the parts about the other outlet become
warmer ;
therefore the heat now has a stronger tendency in
the new direction, seeking
its own affinity, and impels the air by
the other passage
: and this, undergoing the same change and
reproducing the same process, is thus by these two impulses
converted into a wheel swaying backwards and forwards, and so
it
gives rise to respiration.
XXXVII. In the same direction are we to look for the
phenomena of medical cupping-glasses and
explanation of the
of swallowing and of projected bodies, whether cast through the
air or moving along the ground ; and of sounds too, which
from their swiftness and slowness seem to us shrill or deep,
of attraction exercised by amber and the
loadstone. All these diverse phenomena
are due to the manifold interaction of
these two principles the absence of void,
which is the cause of the circular impulsion,
and the vibratory motion which
causes every substance to strive towards
its own peculiar region in space.
8. irtpl TOS larpiKas criKvas] Plato
now applies his two great dynamical
principles to the explanation of various
natural phenomena. He does not work
out the mode of their operation in detail,
but leaves that to be done by the reader.
A full
commentary on the present chapter
will be found in Plutarch quaestiones
platonicae vii. The explanation of the
cupping instruments is this. When the
cup is applied to the flesh, the air within
it becomes warmed and consequently dilated
;
and escaping through the pores of
the metal, it thrusts the surrounding air,
which in its turn, pressing on the surface
of the body, forces the humours to exude
into the :
cup
cf. Timacits Locnis 102 A.
9. TO. TTJS Ka,Tair6