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THE KICIITEENTH CENTUR}' 319

ot the Tooth Hke raws, lie hrhcxts it to he entiith inorganic, as it is
ahsolutch- inipossihle to comeit it into animal iiuiciis. TIk- tooth is
constituted tor the most part h\- a long mass (it is thus he calls the dentine),
which is, however, much harder and denser than an\ other hone. This
part ot the tooth is formed of concentric lameihe, and is \ascidar, as is
proved by the exostosis of the roots and the adhesions that e.xist at times
between the roots and the alveoli. Hunter gives a good description of
the pulp cavity and of the pulp itself. He studied odontogenx with great
care, as is demonstrated b\ his special researches on this point. Ik-
admits the existence of distinct germs for the enamel and for the dentine.
According to him the incisors are formed from three points of ossitication,
the canines from one, and the molars from three or four. The tooth after
its eruption is an e.xtraneous bod\- "with respect to a circulation through
its substance, but the\- have most certainh- a living princijile b\ which
means the\- make part of the bod\-, and are capable of uniting with an\
part ot a living body." The milk teeth, sa\ s Hunter, are not shed by a
mechanical action of the second teeth, but b\' an organizing law of Nature.
The physiology of the masticatory apparatus is treated b\- Hunter with
great accuracy and most extensively. This author combats, by man\-
arguments, the opinion that the teeth grow continualh ; he explains the
apparent lengthening ot those teeth whose antagonists are wanting, b\ the
tendenc\' ot the alveoli to till up, which, however, is not possible in normal
conditions, because ot the constant pressure exercised upon the teeth b\'
their antagonists.
Caries, sa\s Hunter, is a disease of altogether obscure origin; it is not
owing to external irritation or to chemical processes, and seems to be a
morbid form altogether peculiar to the teeth. Onh" in \er\ rare cases
does it attack the roots of the teeth. It rarel\- appears alter Htt\- vears of
age. Hunter does not admit that this disease mav be communicated bv
one tooth to another. As to its treatment, the caries, if superficial, may
be completely removed b\- filing the decayed part of the tooth before the
disease penetrates to the cavit\-, and its spreading will thus be arrested
for, a time at least. In cases where the caries penetrates to some depth,
w-itnptit, however, the destruction of the crown of the tooth being so
extensive as to render it useless. Hunter believed the best mode of treat-
ment to be extraction and replanting of the tooth after having subjected
it to boiling in order to cleanse it perfectly and to destroy its vitality entirely,
this being, according to him, the mode of preventing the further destruction
of the tooth, which once dead can no longer be the seat of an\' disease.
If, instead, one wishes to have recourse to cauterization of the nerve, it
is necessar\' to reach as far as the apex of the root; which, however, is
not always possible. This is a very important point, for no one before
Hunter had yet affirmed the necessit\' of entirely destroying the diseased