Page 46 - My FlipBook

26 ral History of the Tteth.
is thus gradually separated from the old one, both by being
itself more and more deeply excavated in the substance of the
bone, and also by a deposiiion of a bony partition between
them ; thus the rudiment of the permanent tooth is at length
shut up in its own proper socket. There is not however, even
now a total disunion between the two teeth, for as the tempo-
rary one grows and rises in the jaw, tbe connecting cord or
peduncle elongates; and although the sack from which it is
derived, by degrees becomes absorbed, it still remains attached
to the neck of the temporary tooth,* even long after the latter
has pierced the gums; and this connexion between the tempo-
rary tooth, the permanent rudiment and the gum, is thus kept
up by means of the cord, through a small opening in the top
of the new alveolus, which is seen perforating the alveolar
process, immediately behind each temporary tooth."
It is impossible to give a correct idea of this curious process
of nature without plates. The permanent incisores and cus-
pidati, derive their rudimental processes from the same tempo-
rary teeih, and are formed above them in the upper jaw,
and below them in the lower. The permanent bicuspides
are formed underneath the temporary molares, from which they
spring. The second permanent molares derive their rudiments
from the first, and the third, or wisdom teeth from tbe second.
The first permanent teeth which begin to be formed, are the
anterior molares ; at the lime of birth ossification has com-
menced on their extreme points; and between six and seven
years of age, they generally make their appearance. When a
child has cut all its temporary teeth, considerable progress has
been made in the ossification of the permanent incisores, as
well as the first molares. Between two and three years of age
the child has cut all its temporary teeth ; at about six years,
the permanent incisores and first molares are very far advanced
in their formation ; and if none of the temporary teeth have
fallen, there are at this time, no less than forty-eight teeth

* This circumstance is of importance in the m magement of the second
dentition, and will be mentioned under that head.