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At the time of birth, the bodies of ten teeth are distinctly
formed in each jaw ; these are the teeth designed to serve
during the years of childhood, and are commonly called the
temporary, shedding, or milk-teeth.
These temporary teeth, which constitute the first set, are
twenty in number, and are divided into three classes, inciso-
res, cuspidati, and molares, and the teeth on one side of the
mouth, correspond in figure with those of the other, so that
they are situated in pairs.
Besides these twenty teeth, there are in a very early stage
of their formation, the rudiments of some other teeth, which
are to form part of the permanent or adult set. After birth,
as the ossification goes on, the teeth become too long to be
contained within the alveolar cavity, they therefore begin to
make pressure upon those parts which cover them ; this pro-
duces the process of absorption, which proceeds with the en-
largement of the tooth, first removing the membranes which
enveloped the teeth, and afterwards the thick gum which
covered them, this gradually becoming thinner and thinner,
till at length the teeth are suffered to pass through.
There is considerable variety as to the precise time when
the teeth begin to make their appearance. This frequently
seems to depend upon the health and vigour of the child
;
for sometimes the first tooth comes as early as four or
five months ; while, on the contrary, in those of more
delicate and weakly constitutions, no tooth makes its appear-
ance until the child is ten or twelve months old ; and it is not
very uncommon for a child to be turned of fourteen months
before any tooth appears.