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40 INTRODUCTION.

and the pulp ; their crowns depend chiefly for vitality
upon the internal organism, as is evident from the
total loss .of sensibility in them immediately after the
destruction of the pulp.
Necrosis of the teeth differs from that of the other
bones in some particulars, one of the most obvious of
which is, that in the former there is no exfoliation,

the living structure not having the power to throw
off the dead or necrosed portion. Again, a dead part
in contact with the living, does not materially affect
it. The roots of the teeth depending for their vi-
tality upon both their internal and their external
connections, the former of these connections may

be destroyed, without materially affecting the latter.
Thus, a tooth may be partially necrosed,—that is,
vital in one part and dead in another,—without im-
mediate injury to the living portion, and without
separation of the living from the dead. It is a happy
provision that the analogy between the teeth and
the other bones does not, in this respect, obtain ; for
if it did, we should find the crowns of the teeth sepa-
rated from the roots in all cases, immediately after
the death of the pulp.
There results but little change of color to the teeth
from necrosis, unless coloring matter is absorbed by
the dentine from the decomposed pulp; though of

course the lifelike lustre and appearance of the