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DYSTROPHIES OF THE TEETH. 19

only as far as shown in the lower section of Figure 20, and had
the broad conical opening shown at b. The internal diameter
at the point to which the end of the apical portion reaches was of
the size shown by the end of that piece. The result was that the
solid dentin formed at that time represented only the lower
square end of the upper piece. This was broken in the effort
to extract and the root pulled apart on the line of the area of
interglobular spaces, the line representing the lines of the proc-
ess of growth.
The patient failed to keep his appointment for further treat-
ment and was not seen again. The opportunity to inquire into
the nature of the nutritional disturbance that had caused this
rare form of injury was lost. The specimen, however, tells its
own story clearly. This case shows that the root of a tooth may
also be injured by a condition of malnutrition, though such an
extreme occurrence as this must be rare.
I have noted a considerable number of cases in which a zone
of injury occurred in the dentin beginning below the gingival
line, as in the case shown in Figures 19, 20, though they are far
more rare than those occurring in the crown of the tooth.
Figure 21 represents another case of injury of the graver
sort, occurring in a central incisor, in which but little discolor-
ation is apparent. The wide overlapping of the new onto the
older enamel, the complete breakage of the enamel rods along the
line of junction of the two, the change in the course of the enamel
rods in the two formations of enamel and the profound disturb-
ance of and recurving of the labial dento-enamel junction, all
point to a long suspension of nutrition and account for the grave
distortion of the form of the tooth. This is much like that shown
in Figure 12. The line of interglobular spaces is sharp and
severe, but very narrow, and the dentin is normal immediately
on either side. The incisal edge had been ground away in the
endeavor to improve tbe appearance before the tooth, with the
other incisors, was extracted. About one-third of the normal
length of the crown had been missing.
The next case is very curious in several respects. It is a
bicuspid tooth that showed a very slight groove in the enamel
not far from the gingival line. It was covered by the overlap-
ping gum margin, except on the buccal surface. The whole tooth
was, perhaps, as white as any normal tooth and was without any
discoloration along the line of the groove, except that caused
by a deposit of dark, closely adherent serumal calculus at several
points. A photograph of this groove was but a partial success,
as is shown in Figure 22. The tooth was then divided mesio-
distally, preparatory to grinding sections. In examining the