The time when, and the manner in
which the first set appear has been pointed out. Now although these
admirably answer the purposes for which they were given up to the
seventh year, after this period they fail to do so: they are not
sufficiently numerous,--in their structure they are not strong or
durable,--nor is their power of mastication sufficiently great.
They are not sufficiently large or numerous. If the mouth of a child
at this age is examined, it will be seen, that a considerable interval
has taken place between the teeth in consequence of the growth and
expansion of the face; hence a larger set has become necessary to fill
the arch. But it may be asked, do not the teeth grow with the growth of
the body? and if not, why is it so? They do not, and for this reason:
the important office which these organs are destined to perform requires
that they should be composed of a substance too dense and of too low
an organization to allow of any subsequent growth and enlargement. Thus
the size of the teeth is determined and acquired before they make their
appearance through the gums. This being the case, it will be readily
seen, that the teeth which would be of appropriate size in the mouth of
the infant, would be quite inadequate to the enlarged dimensions of the
adult; hence the necessity of a second set, exceeding in number, and
size the teeth of the first.
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