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lie observes have no roots, could perform all these violent
efforts, so as to burst through this membrane. Even Mr.
Hunter says,* " When the tooth cuts the gum, this mem-
brane or capsula is likewise perforated, after which it begins
to waste." Others are of opinion, that the membrane being
lacerated, the body of the tooth passes up through it, and
that it afterwards becomes the periosteum of the root. From
what I have already said, the impossibility of a tooth burst-
ing or rising through its membrane will be readily perceived,
for as it is firmly united to the neck of the tooth, it must take
of the same precise motion with the tooth, and therefore
must, after such motion of the tooth, retain the same relative
#
position towards it as before. So that the disappearance of
the membrane is not owing to a rupture of it, but to a wasting
or absorption of it, in proportion as it has perfected the cor-
tex striatus.
This fact will be more fully explained, when we come to
speak of the teeth of animals in general. I have seen the
ragged edges of the membrane, appearing above the level of
the ffum ; a similar appearance was no doubt observed by
Herissant, though he attributed it to a wrong cause.
Galen, Eustachius, and others, were of opinion that the
upper teeth appeared sooner than the under ; they were
fully aware, however, that they appear irregularly and at
different periods. Mr. Hunter describes their appearance in
the following words.f " The incisores begin to cut or pass
through the gums ; first, generally, in the lower jaw ; but the
cuspidatus and molares of the fetus, are not formed so fast
as the incisores ; they generally all appear nearly about the
same time, viz. about the twentieth or twenty-fourth month :

* Natural History, page 87. t Natural History, page 78.