Page 74 - My FlipBook

54 Inaugural Dissertation.
First—The teeth of young rabbits are colored red, in three
or four weeks after the commencement of their diet.
Second—If the madder be now omitted* for ten weeks; at the
end of this time, the coloriug is absorbed, and the teeth regain
their natural white color.
Third—The teeth of old rabbits, fed with madder during
four months are considerably tinged with the dye through their .
whole bony structure.
We do not attach very great importance to these experi-
ments, as it is evident from the structure and formation of the
teeth of rabbits, that their growth is continuous as in the squir-
rel tribe ; yet we think they serve to invalidate the experi-
ments of Mr. Hunter, before mentioned.
Again he says, " another circumstance in which the teeth
seem different from other bones, and a strong circumstance in
favor of their having no circulation within them is, that they
never change by age, and seem never to undergo any change
but by abrasion ; they do not grow soft as other bones do, as
we find in some cases when the earth)- matier has been taken
into tHfe constitution."
That the teeth do not undergo any change when completely
formed, but by abrasion, is an assertion not founded on ob-
servation.
" It is always observed that as persons advance in life, their
teeth lose that whiteness which they possessed in the time of
youth. This change in the appearance of the teeth seems to
depend upon one which takes place in iheir cavities, by which
the vessels entering them are gradually destroyed, and the
supply of blood proportionally diminished. In the teeth of
persons advanced in years, the cavity is very frequently oblite-
rated, in consequence of a deposit of bony matter, which en-
tirely desiroys the internal organization. When this happens,
the teeth alwa}-s lose their color, and become very yellow,
their texture also becomes more brittle, and they acquire a
horny transparency."—Fox' Natural History of the Teeth,
Part II, page 24.