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DYSTROPHIES OF THE TEETH. 31

and an exploring tine enters the enamel without difficulty. Such
spots as these latter are rare. Sometimes such a spot shows
discoloration about its central portion or radiating through it
in irregular lines or blotches. The smaller white spots covered
with the glazed membrane are common in any great school clinic
where large numbers of persons are present for dental oper-
ations.
A histological examination of these shows the enamel rods
to be normal in their formation and continuous with the rods
deeper in the enamel, which is altogether normal in form and
color. Generally the smaller white spots that appear on the sur-
face of the enamel do not extend through its thickness. It often
ends abruptly in a line following the incremental lines of enamel
formation, i. e., the lines of Retzius, as seen in Figures 36, 37.
In the area of the white spot there is no cementing substance
between the enamel rods. This is the histological characteristic
of all of these white spots that I have yet examined. This is,
therefore, a dystrophy affecting the formation of the cementing
substance between the enamel rods the same as certain of the
pits in the enamel are a dystrophy of the enamel rods.
White Enamel.
I received fourteen teeth from Dr. D. J. McMillen, of Kansas
City, which had been extracted by Dr. John Prunty, of Boyd,
Texas, for one patient, all of which were deformed in what, from
macroscopic examination, seemed a similar manner to that
described in Dr. Callow's case. The teeth were very dirty with
blood stains and from being handled, which obscured some of
their most notable characters. But a closer examination showed
the enamel to be soft. I found that it could easily be picked
to pieces, and evidently much of it had been lost in this way since
the teeth were extracted. The axial surfaces were made up of
irregularly formed spiculse that rendered them extremely rough.
Many of these had been broken, so much so, indeed, that it was
with some difficulty that I was able to get sections showing the
condition at the time the teeth were extracted.
When I came to the making of sections of these, I found the
enamel white through its entire thickness, not the white bluish
color of enamel, but the white color of unglazed white paper.
The enamel had seemed so frail that I had soaked the teeth in
thin balsam and then thoroughly dried them, in order to retain
the spiculse of enamel.
This case proved to be something entirely different from
Dr. Callow's case, histologically. The dento-enamel junction
was perfectly normal in all its parts. Next to the dento-enamel