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18 MACROSCOPIC ANATOMY OF Till': HUMAN TEETH.
fused together. Thus iu uinu the incisors arc formed oi' a sin<2;le cone, the
truncated apex of which is compressed to form the wide cutting- edge (Fig.
1, (f). The canine or cuspid is a single cone, the apex of which is com-
pressed into a trihech'al point, or pointed pyramid (b). The bicuspids
are composed of two coiu^s fused together, the forms of the cones being
(piitc distinct the entire k'ugth of the tooth, as iu the upper bicuspids (c).
The typal upper molar is formed by the addition of the third cone to
the l)icuspid form, as ])lainly noticed in the three roots and the primitive
The usual ([uadrieuspid form is made by the addition
three cusps ((/).
of a cingule. The lower molar consists of four cones, which may be
plainly distinguished by an analysis of its elements {e). Each cone in
the structure of a tooth is surmounted by a cusp or tubercle. Extra cusps
above the number of primary cones are but cingules or undeveloped cusps.
In the genesis of tooth forms, therefore, the complex teeth, as the
bicuspids and molars, are formed by the repetition and addition of cones
and their accompanying cusps, both laterally and longitudinally of the jaw.
4. The Dental Arch.—The teeth of man are arranged around the
margins of the upper and lower jaws in close contact, and have no
Fig. 2.
Square. Rounded Square. Rounded. Rounded V.
The main types of the dental arch.
interspaces between them. The basal arch is a graceful parabolic curve,
with some variations which lead from the round arch to the incomplete
parallelogram or even to a w^ell-defined V shape. These variations may
be classified as follows
First: The square arch (Fig. 2, a). This is found usually in
persons of strong osseous organization, of Scotch or Irish descent i. e.
of Gaelic extraction—and is probably derived in the first instance from
a dolichocephalic people. The squareness is more or less dependent
upon the prominence of the large canines, which stand out very
markedly at the angles of the square. The incisors present a flat front
and project slightly, with little or no curve of the incisive line.
The bicuspids and molars fall backw\ard from the canines with no per-
ceptible curve. The two sides are quite parallel, but sometimes there
may be a slight divergence toward the cheek at the rear. This is the
low form of arch which appears in the apes and some low races.
18 MACROSCOPIC ANATOMY OF Till': HUMAN TEETH.
fused together. Thus iu uinu the incisors arc formed oi' a sin<2;le cone, the
truncated apex of which is compressed to form the wide cutting- edge (Fig.
1, (f). The canine or cuspid is a single cone, the apex of which is com-
pressed into a trihech'al point, or pointed pyramid (b). The bicuspids
are composed of two coiu^s fused together, the forms of the cones being
(piitc distinct the entire k'ugth of the tooth, as iu the upper bicuspids (c).
The typal upper molar is formed by the addition of the third cone to
the l)icuspid form, as ])lainly noticed in the three roots and the primitive
The usual ([uadrieuspid form is made by the addition
three cusps ((/).
of a cingule. The lower molar consists of four cones, which may be
plainly distinguished by an analysis of its elements {e). Each cone in
the structure of a tooth is surmounted by a cusp or tubercle. Extra cusps
above the number of primary cones are but cingules or undeveloped cusps.
In the genesis of tooth forms, therefore, the complex teeth, as the
bicuspids and molars, are formed by the repetition and addition of cones
and their accompanying cusps, both laterally and longitudinally of the jaw.
4. The Dental Arch.—The teeth of man are arranged around the
margins of the upper and lower jaws in close contact, and have no
Fig. 2.
Square. Rounded Square. Rounded. Rounded V.
The main types of the dental arch.
interspaces between them. The basal arch is a graceful parabolic curve,
with some variations which lead from the round arch to the incomplete
parallelogram or even to a w^ell-defined V shape. These variations may
be classified as follows
First: The square arch (Fig. 2, a). This is found usually in
persons of strong osseous organization, of Scotch or Irish descent i. e.
of Gaelic extraction—and is probably derived in the first instance from
a dolichocephalic people. The squareness is more or less dependent
upon the prominence of the large canines, which stand out very
markedly at the angles of the square. The incisors present a flat front
and project slightly, with little or no curve of the incisive line.
The bicuspids and molars fall backw\ard from the canines with no per-
ceptible curve. The two sides are quite parallel, but sometimes there
may be a slight divergence toward the cheek at the rear. This is the
low form of arch which appears in the apes and some low races.
