quickly; the seed is a residue, and further, by being lost, it

produces dryness. Hence the mule lives longer than either the horse or

the ass from which it sprang, and females live longer than males if

the males are salacious. Accordingly cock-sparrows have a shorter life

than the females. Again males subject to great toil are short-lived

and age more quickly owing to the labour; toil produces dryness and

old age is dry. But by natural constitution and as a general rule

males live longer than females, and the reason is that the male is

an animal with more warmth than the female.

The same kind of animals are longer-lived in warm than in cold

climates for the same reason, on account of which they are of larger

size. The size of animals of cold constitution illustrates this

particularly well, and hence snakes and lizards and scaly reptiles are

of great size in warm localities, as also are testacea in the Red Sea:

the warm humidity there is the cause equally of their augmented size

and of their life. But in cold countries the humidity in animals is

more of a watery nature, and hence is readily congealed.

Consequently it happens that animals with little or no blood are in

northerly regions either entirely absent (both the land animals with

feet and the water creatures whose home is the sea) or, when they do

occur, they are smaller and have shorter life; for the frost

prevents growth.

Both plants and animals perish if not fed, for in that case they

consume themselves; just as a large flame consumes and burns up a

small one by using up its nutriment, so the natural warmth which is

the primary cause of digestion consumes the material in which it is

located.

Water animals have a shorter life than terrestrial creatures, not

strictly because they are humid, but because they are watery, and

watery moisture is easily destroyed, since it is cold and readily

congealed. For the same reason bloodless animals perish readily unless

protected by great size, for there is neither fatness nor sweetness