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Anatomy and Physiology of the Teeth. 19
be the seat of the disease, is explained ; hence also the filing
of a saw or any grating noise sets the teeth on edge. The sym-
pathetic pains in the eyes, temples and different part of the
face, caused by diseased teeth, are also explained by the in-
timate connexion existing between the three great branches
of the fifth pair.
Nature has given man (and most mammalia,) two sets of
teeth; the first, temporary or milk teeth, which are intended to
serve during childhood, and the permanent or adult teeth, inten-
ded to last from the falling of the temporary ones to the end of
life. The reasons of this bountiful provision of nature are obvi-
ous, namely, the different size and shape of the jaws, at different
ages, and the peculiar formation of the teeth not permitting an
increase of growth in them, as in other bones. There are
thirty-two adult teeth; sixteen in each jaw; namely, four
incisores, or front teeth, (from the latin incidere, to cut;) two
cuspidati or eye teeth, (cuspis, a spear, spear pointed,) four
bicuspides, or small double teeth, (from bis, twice and cuspis,
two pointed ;) six molares or grinders, (molaris, a mill-stone.)
The last molar teeth in each jaw are called lyisdom teeth,
(dentes sapiential,) because we generally get them about eigh-
teen or twenty years of age, or the age of full maturity.
There are twenty temporary teeth, ten in .each jaw ; four
incisores, two cuspidati, and four molares.
It is unnecessary to give a particular description of each
tooth, as every one knows more or less of the shape of the
teeth from observation.
The incisores are somewhat wedge shaped, widest at the
cutting edge and gradually diminishing towards the neck ;
they are slightly concave externally and convex internally,
but the concavity is interrupted by a tubercle near the neck.
They are situated in the anterior part of the jaws, and form
the centre of the maxillary arch ; each has but one fang. The
central incisores of the upper jaw are much larger than the
lateral incisores adjoining them. The incisores of the lower
jaw are much smaller than those .of the upper, and nearly re-
semble each other in shape.