Page 115 - My FlipBook

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It will be proper in this place to observe the manner in
which the jaw bones grow, (the under one being taken as an
example,) and to point out the difference between the tem-
porary and permanent teeth.
After a child has obtained all the temporary teeth, the jaw,
in general, grows very little, in the part which they occupy.
In those children who are an exception to this rule, the tem-
porary teeth become a good deal separated from each other,
and these are the cases in which the shedding of the teeth is
effected without the assistance of art. When the jaw of a
child is compared with that of an adult, a very striking dif-
ference is observed ; that of a child forms nearly the half of
a circle, while that of an adult is the half of a long ellipsis.
This comparison clearly points the part in which the jaw re-
ceives its greatest increase, to be between the second tempo-
rary molaris and the coronoid process ; and this lengthened
part of the jaw is destined to be the situation of the perma-
nent molares.
By the elongation of the jaw, a great change in the form
of the face is produced ; that of a child is round, the cheeks
are plump and the chin flat ; in the adult the face is more
prominent with a flatness of cheek and a considerable
length of chin.
The temporary incisores and cuspidati are much smaller
than the permanent, while the molares of the temporary set
are larger than the bicuspides which succeed them. Hence
it is that the incisores and cuspidati are so frequently irregu-
lar, and they never could be otherwise, were it not that some
space were gained from the molares, in consequence of the
bicuspides being much smaller. This circumstance is ren-
dered intelligible, by examining jaws at various ages, and
observing in what particulars they differ from each other.
Until about twelve months after birth, the jaw grows uni-
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