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as were formed while the animal 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 differ-
ent in all other bones ; for we know that any part of a bone
which is already formed, is capable of being dyed with mad-
der, though not so fast as the part that is forming ; there-
fore, as we know that all other bones, when formed, are vas-
cular, 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 farther ; if you feed a pig with madder for
some time, and then leave it off for a considerable time be-
fore 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 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 differ-
ent from that of the other bones. Bones begin at a point,
and shoot out at their surface ; and the part that seems al-

* Hunter. Nat Hist, of the Human Teeth, page 39.