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THE MOLARS. 45

the European races. The tubercles are symmetrical, rounded and
obtuse, the lingual being, however, sharper than the buccal.
The sulci describe a cruciform shape, separating the four tubercles
symmetrically from each other. The buccal groove sometimes continues
on to the buccal face, rarely to the lingual. The triangular grooves
run up on the morsal triangular ridges. The marginal ridges are well
marked, the mesial and distal being often divided by grooves. The
triano-ular ridges are usually w^ell marked, leading to the centre of the
tooth. They are full and strong.
The buccal face (d) is convex and of more regular form than that
of the first molar. It is divided into two lobes {e, e) by the buccal

Fig. 25.

h h
The lower second molar.

groove {d), which is rarely deep. A pit is often found in the centre
of the face, which may become the seat of caries. The face is curved
toward the centre of the tooth, as in the first molar.
The lingual face is similar to that of the first molar, but may be more
rounded toward the morsal l)order. It is symmetrically convex in both
directions.
The )iic.- excei)t tluit, the crown being smaller, they may be more perpendicular,
but are well rounded.
The neck (g) is more regularly formed than tliat of the first molar,
the margin of the enamel line being quite as irregular. It may be more
constricted.
The roots {h, It) are similar to those of the first molar, but are more
rounded in shape, are usually crooked, and on that account difficult to
treat.
The jiidp cancds arc similar to those of the first molar, but the tend-
ency to crookedness renders treatment quite difficult. The direction
of irregularity of form is so uncertain that no rule can be applied to it.
17. The Third Molars.—The up])er and lower third molars can best
be described together, on account of their similar eccentricities. They
are verv irregular as t(t the time and to the frecpiency of their appearance
in civilized man. About one-half of the individuals of European races