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PATHOLOGY OP THE HABD TISSUES OF THE TEETH.

ATROPHY OF THE TEETH.

ILLUSTRATIONS: FIGURES 1-47.
THE term "atrophy" includes two distinct ideas; the one is
a failure of the development of a local part because of a fail-
ure of nutrition, the other is a wasting of a part because of a local
failure in the nutritive processes. Atrophied teeth belong to
the first class ; they have never been fully formed. They come
through the gums in the condition of deformity in which they
are afterward seen, and do not, as some seem to suppose, waste
away after having taken their places in the arch. The deformity
is a result of incomplete formation. The term "hypoplasia"
has of late been widely used in the German language in the same
sense and is being adopted by some writers in English. The
author has preferred to use the older term which has been used
to designate this condition since it was first spoken of in the
English language.
In the human teeth there is no process of repair and the
deformity is permanent. Similar phenomena occur in the finger
nails and the hair. During an illness that interferes seriously
with nutrition, the portion of the finger nail then forming will
be dwarfed, which will appear later as a groove across the nail.
This, like the marking of the teeth, is not remedied by any repar-
ative process. But the nail is continuously growing and the
groove moves on over the length of the nail and disappears.
During a severe illness that interferes with nutrition, a sec-
tion of hair is imperfectly formed, and when in the process of
growth this section arrives at the surface of the skin and is sub-
jected to bending, it breaks and the hair suddenly falls away
These are conmion phenomena following severe cases of typhoid
fever. The hair follicles are not injured and the hair is replaced
by the regular process of growth.
In the continuously growing teeth of the rodents such an
injuiy would be finally removed and remedied in the same way
as the grooving seen upon the finger nails, but this can not occur
in the human teeth.
The deformity, though much varied in different cases, is,
when closely analyzed, always similar in character. It always