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

their natural heat elaborate and concoct the nutriment, the

governing organ takes the chief share in this process. Hence, though

the other members become cold, life remains; but when the warmth

here is quenched, death always ensues, because the source of heat in

all the other members depends on this, and the soul is, as it were,

set aglow with fire in this part, which in sanguineous animals is

the heart and in the bloodless order the analogous member. Hence, of

necessity, life must be coincident with the maintenance of heat, and

what we call death is its destruction.



5



However, it is to be noticed that there are two ways in which fire

ceases to exist; it may go out either by exhaustion or by

extinction. That which is self-caused we call exhaustion, that due

to its opposites extinction. [The former is that due to old age, the

latter to violence.] But either of these ways in which fire ceases

to be may be brought about by the same cause, for, when there is a

deficiency of nutriment and the warmth can obtain no maintenance,

the fire fails; and the reason is that the opposite, checking

digestion, prevents the fire from being fed. But in other cases the

result is exhaustion,-when the heat accumulates excessively owing to

lack of respiration and of refrigeration. For in this case what

happens is that the heat, accumulating in great quantity, quickly uses

up its nutriment and consumes it all before more is sent up by

evaporation. Hence not only is a smaller fire readily put out by a

large one, but of itself the candle flame is consumed when inserted in

a large blaze just as is the case with any other combustible. The

reason is that the nutriment in the flame is seized by the larger

one before fresh fuel can be added, for fire is ever coming into being

and rushing just like a river, but so speedily as to elude

observation.