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50 HUNTER ON THE TEETH.

OF THE SITUATION OF THE TEETH.
The general shape and situation of the Teeth are obvious, (z)
The opposition of those of the two Jaws, and the circle which
each row describes, need not be particularly explained, as they
may be very well seen in the living body, and may be supposed
to be already understood, from what was said of the Alveolar
Processes.
We may just observe, with regard to the situation of the two
rows, that when they are in the most natural state of contact,
the Teeth of the Upper-Jaw project a little beyond the lower
Teeth, even at the sides of the Jaws ; but still more remark ably
at the fore part, where in most people the upper Teeth lie before
those of the Lower-Jaw : and at the lateral part of each row,

fact that osseous union is never observed between the tooth-fang and
the alveolus. (1) Mr Hulme, in his published Lectures on Diseases of
the Dental Periosteum, adduces the case of some herbivorous quadru-
peds, as for instance the common Ox, in which the distinction of the
layers is easily shown in support of a similar view. The latter author
does not allow that the layer covering the fang is merely a reflection
of that lining the socket : he believes, with Mr Bate, that there is a
distinct origin for each membrane. " The alveolus," he writes, " is
provided with its periosteum long before the crown of the tooth is
completed ; whereas in the tooth there is no periosteal layer until the
formation of its fang and its investing layer of cement. At the period
when the fang of the tooth is about to be formed, the sac of the tooth-
germ becomes adherent to the neck of the tooth ; its outermost layer
continues to grow in the same ratio as the fang, and becomes the
formative organ of the cement. When the tooth is completed, this
membrane still remains, and constitutes its periosteum. At the apex of
the fully-developed fang, the periosteum of the tooth becomes intimately
associated with that of the alveolus, and the contiguous surfaces of the
two membranes are connected together by the passage of blood-vessels
and nerves." (2) Kolliker states that the alveolar periosteum is suiter
than that of other bones, that it contains no elastic elements, but rich
plexuses of nerves having thick nerve-tubes. (3)]
(2) [In the class Mammalia, true teeth implanted in sockets are

(1) On the Peridental Membrane, in its relation to the Dental Tissues, -
British Journal of Dental Science, vol. i., p. 7.
(2) Dental Review, vol. hi., p. 203.
(13) Kolliker, op. cit., loc. cit.