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OF THE FORMATION OF THE TEETH IN THE FXETUS, — 117
pulpy substances become more distinct; the anterior of which

kow (1) before the publication of Goodsir's observations had contradicted
those of Arnold; and more recently M. Natalis Guillot has given an
entirely different account ofthe formation of the tooth follicles, in which
he denies their origin on the surface of the mucous membrane, neither
does he admit that they depend on any folding of the mucous membrane
which has carried the germ from the surface into the cavity of the alve-
olus.(2) More recently the researches of Robin and Magitot have led them
to a similar conclusion. According to these observers the dental follicles
and bulbs originate in the Bnbmucous tissue which extends to the bottom
of the osseous groove in the maxillaries. The term follicle is made to
include the bulb, the organ of the enamel and the follicular wall ; of
these parts the bulb originates first, then the follicular wall, which sub-
sequently closes over, and, lastly, the organ of the enamel as soon as the
follicle is closed. The follicles of the lower jaw precede those of the
upper. In the human foetus the appearance of the follicles is nearly in
the same order as the eruption of the corresponding teeth in each jaw.
The internal incisor and the anterior molar first. These are followed
closely by the external incisor, then the posterior molar, and, lastly, the
canine. The changes which take place in the dental follicles follow an
order in accordance with that of the appearance of the follicles, i.e., in
the follicle which appears first the follicular wall closes first, the organ
of the enamel appears first, the ivory and enamel originate first. The
first follicle in the lower jaw appears about the sixtieth day, that in
the upper about the sixty-fifth day. The number of follicles of the first
dentition in the lower jaw is complete about the seventy-fifth day ; in
the upper jaw about five days later. The follicles of the first permanent
molars appear in the lower jaw about the eighty-fifth day ; in the upper
from the ninetieth to the ninety-fifth. The follicles of the teeth of
replacement appear, some a little before birth or sometimes later, the
others at longer or shorter intervals after birth. The bulbs do not com-
mence close to the dental vessels and nerves, but a little above them in
the thickness of the submucous tissue, nearly at the middle of the depth
of the groove. The base of the follicle, as the organ -rows larger, be-
comes nearer to the vessels and nerves.
The phenomena of the genesis and completion of the follicles have
been minutely described by Robin and Magitot. The following are the
principal steps of the process as observed by them :—A little before the
first appearance of a follicle, that point of the submucous tissue at

(1) For an account of Raschkow's paper, see Xasinyth's "Historical Intro-
duction."
(2) Ann. des Sciences Nat. Ser. iw, T. ix. (1858), and Dental Rev.,
vol. ii., p. 401
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