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OF THE PERIOSTEUM OF THE TEETH. 55

OF THE PERIOSTEUM OF THE TEETH.
The Teeth, as we observed, are covered by an Enamel only
at their bodies ; but at their fangs they have a Periosteal)),
which, though very thin, is vascular, and appears to be common
to the Tooth which it incloses, and the socket, which it lines as
It covers the Tooth a little
an investing internal membrane, (y)
beyond the bony socket, and is there attached to the Gum.
twigs, 0-OT" to 0-Q2"'. These ascend into the pulp cavity without
forming at first considerable anastomoses, but giving off separate
fibrils. On reaching the thicker part of the pulp, they form a rich
plexus " with elongated meshes and collections of nerve tubes, and thus
gradually break up into tine primitive fibres, O'OOl'" to 0-0016'" in
diameter." These primitive fibres form evident loops, but it is uncer-
tain whether they represent the absolute terminations. (1) Mr Tomes
states that he has been unable to trace any connection between the
ultimate nerve fibres of the pulp and the dentinal fibrillse which be
describes. (2)
It would appear that at least in some instances the size of the nerve
supplying the tooth-pulp is proportionate to the size and importance
of the tooth. Thus Professor Owen notices the large size of the
nerve supplying the laniary in the Dog and other Carnivora. In the
Boar, he observes that the nerve supplying the developed tusk is still
larger, having relation not oidy to the size of the tooth, but also to the
continual reproduction of the matrix at its base. (3)]
(y) [A difference of opinion appears to exist between writers on the
subject of the dental periosteum. Hunter, Bichat, and Kblliker
describe but one layer of periosteum as common to the tooth and the
socket. The latter author writes, "the periosteum of the alveoli is
very accurately applied to the surface of the fangs." Other observers,
amongst whom are Fox, Bell, Spence Bate, and Hulme, believe that
the periosteum consists of two layers—one lining the alveolar cavity,
the other covering the fang. Mr Bell asserts that he has frequently
removed a tooth in the dead subject, and found not only the
Mr Spence
fang covered, but the socket lined with periosteum. (4)
Bate applies the term " peridenteum" to the layer covering the
fang, to distinguish it from the periosteum of the alveolus. He
regards the peridenteum as a dermal tissue distinct in origin from the
periosteum, and on their complete separation, he believes, depends the
Kolliker, op. cit., p. 300.
(1)
(2) Tomes, Manual of Dental Surgery, p. 286.
(3) Odontography, Introduction, p. lxvi.
(4) The Anatomy, Physiology, and Diseases of the Teeth, byT. Bell, F.R.S.,
p. 43, 2nd edition.