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52 HUNTER ON THE TEETH.
parts of its Teeth formed before the feeding with madder, those
parts will be known by their remaining of this natural colour ;
but such parts of the Teeth as were formed while the ani-
mal was taking the madder, will be found to be of a red colour.
This shews, that it is only those parts that were forming while
the animal was taking the madder that are dyed ; for what were
already formed will not be found in the least tinged. This is
different in all other bones ; for we know that any part of a
bone which is already formed, is capable of being dyed with
madder, though not so fast as the part that is forming ; there-
fore as we know that all other bones when formed are vascular,
and are thence susceptible of the dye, we may readily suppose
that the Teeth are not vascular, because they are not susceptible
of it after being once formed. But we shall carry this still
if you feed a pig with madder for some time, and then
farther ;
leave it off for a considerable time before you kill the animal,
you will find the above appearances still subsisting, with this
addition, that all the parts of the Teeth which were formed
after leaving off feeding with the madder will be white. Here
then in some Teeth we shall have white, then red, and then
white again ; and so we shall have the red and the white colour
alternately through the whole Tooth.
This experiment shews, that the Tooth once tinged, does not
lose its colour ; now as all other bones that have been once
tinged lose their colour in time, when the animal leaves off
feeding with madder (though very slowly) , and as that dye must
be taken into the constitution by the absorbents, it would seem
that the Teeth are without absorbents, as well as other vessels.
This shews that the growth of the Teeth is very different from
that of other bones. Bones begin at a point, and shoot out at
their surface ; and the part that seems already formed, is not in
reality so, for it is forming every day by having new matter
thrown into it, till the whole substance is complete ; and even
then it is constantly changing its matter.
Another circumstance in which Teeth seem different from
bone, and a strong circumstance in support of their having no
circulation in them, is that they never change by age, and seem