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The enamel when broken appears to be composed of a
greater number of small fibres, all of which are so arranged
as to pass in a direction from the centre to the circumference
of the tooth, so as to form a sort of radii round the body of the
tooth. This is the crystalized form it acquires some time
after its deposit ; by this disposition of its fibres, the enamel
acquires a great degree of strength, and thus it is not so
readily worn down in mastication, nor so easily fractured by
violent action of the teeth.
While some eminent physiologists have contended, that
the teeth, when they have attained their full growth, are to
be considered extraneous bodies, and that they no longer re-
ceive nutriment like the other bones of the body, oth-
ers have supposed, that even the enamel is kept up in
future life by continued deposits : but that this cannot be the
case will be obvious, when it is considered that the mem-
brane which invested the pulp and produced the enamel, is
destroyed before the tooth can appear. When a tooth first
appears, the enamel is thicker than at any other period of
life, and from that time begins to decrease ; this may be re-
marked in some of the permanent teeth. The incisores,
when they first pass through the gum, have their edges
notched, the cuspidati are sharp at their points, and the
grinding surface of the molares is always irregular. This
sharpness of the points of the teeth is occasioned by a larger
deposit upon those parts where ossification had first com-
menced. By the friction of the teeth against each other,
and against the food in mastication, the teeth are worn
smooth, the notches upon the incisores disappear, the points
of the cuspidati are rounded, or in many cases entirely
removed, and the surfaces of the molares become much
smoother.