On Youth And Old Age, On Life And Death, On Breathing   

make them add fire to fire.



11



The theory found in the Timaeus, of the passing round of the

breath by pushing, by no means determines how, in the case of the

animals other than land-animals, their heat is preserved, and

whether it is due to the same or a different cause. For if respiration

occurs only in land-animals we should be told what is the reason of

that. Likewise, if it is found in others also, but in a different

form, this form of respiration, if they all can breathe, must also

be described.

Further, the method of explaining involves a fiction. It is said

that when the hot air issues from the mouth it pushes the

surrounding air, which being carried on enters the very place whence

the internal warmth issued, through the interstices of the porous

flesh; and this reciprocal replacement is due to the fact that a

vacuum cannot exist. But when it has become hot the air passes out

again by the same route, and pushes back inwards through the mouth the

air that had been discharged in a warm condition. It is said that it

is this action which goes on continuously when the breath is taken

in and let out.

But according to this way of thinking it will follow that we breathe

out before we breathe in. But the opposite is the case, as evidence

shows, for though these two functions go on in alternation, yet the

last act when life comes to a close is the letting out of the

breath, and hence its admission must have been the beginning of the

process.

Once more, those who give this kind of explanation by no means state

the final cause of the presence in animals of this function (to wit

the admission and emission of the breath), but treat it as though it

were a contingent accompaniment of life. Yet it evidently has