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THE GREEKS 63

grows older, the teeth hecome darker in color, except in the case of the
horse, whose teeth grow whiter with age.
The last molars are cut b\- men and women about the twentieth year;
hut in some cases, and especialh' with women, the\" have been known
to come forth—not without pam— ver\' much later, even so late as at
eic);ht\' \ears of age.
The man has more teeth than the woman; this peculiarit\- is also to
be found in the female of some animals (such as sheep, goats, and pigs).
Individuals provided with many teeth generally live the longest, those
instead who have fewer teeth (or simpl\- far apart) are generalh- shorter
lived.
The teeth are generated b\- the nourishment distributed in the jaw-
bone; they are, in consequence, of the same nature as bones. Their
surface, however, is ver\' much harder than that ot the bones. The teeth,
contrarih' to all other bones, grow throughout life, so as to provide for
their wearing awa\" through mastication; and tor this reason the\" lengthen
when the antao;onizino; teeth are wanting.^
The teeth differ from all the other bones, therein that the\' are generated
after the body has been already constituted; they are, therefore, secondar\-
formations; and precisely for this reason are able to be shed and to be
renewed.
Some of the veins of the head, says Aristotle, terminate with very
slender branches inside the teeth."
The dental system of the monkey is altogether similar to that of man.
The molar teeth exist in viviparous quadrupeds as well as in man;
in the oviparous quadrupeds and in fish the\' are wanting. They serve
to grind food, a function in which the lateral movements of the inferior
jaw have, in many animals, a large share. For this reason, in animals
who have no molars, these lateral movements do not exist.
In birds, the beak takes the place of the lips and teeth; the substance
of which it is formed is similar to that of the horn or the nails.
In those animals which, instead of having all the teeth sharp, are
furnished with incisors, canines, and molars, these three species of teeth
are disposed in the same order as in man.
The setting on edge of the teeth ma}- be produced not only by eating
acid things, but also simply by seeing them eaten. This sensation may
be made to cease by the use of purslane and salt.

* This, as well as other errors of Aristotle, we shall tind repeated throuuhout the lapse
of centuries by many authors, Galen not excluded, who, in fact, by the authority of his name,
gave them valid confirmation.
* The distinction between arteries and veins was, at that time, not yet well known, thou<;h
we already find, in this passage of Aristotle, allusion made to the relations between the teeth
and the bloodvessels.