8
With regard to the teeth it has been stated previously that they
do not exist for a single purpose nor for the same purpose in all
animals, but in some for nutrition only, in others also for fighting
and for vocal speech. We must, however, consider it not alien to the
discussion of generation and development to inquire into the reason
why the front teeth are formed first and the grinders later, and why
the latter are not shed but the former are shed and grow again.
Democritus has spoken of these questions but not well, for he
assigns the cause too generally without investigating the facts in all
cases. He says that the early teeth are shed because they are formed
in animals too early, for it is when animals are practically in
their prime that they grow according to Nature, and suckling is the
cause he assigns for their being found too early. Yet the pig also
suckles but does not shed its teeth, and, further, all the animals
with carnivorous dentition suckle, but some of them do not shed any
teeth except the canines, e.g. lions. This mistake, then, was due to
his speaking generally without examining what happens in all cases;
but this is what we to do, for any one who makes any general statement
must speak of all the particular cases.
Now we assume, basing our assumption upon what we see, that Nature
never fails nor does anything in vain so far as is possible in each
case.
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