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22 MACROSCOPIC ANATOMY OF THE HUMAN TEETH. ——
6. Number and Classes of the Teeth.—Man has tliirty-tAvo teeth,
divided into four clai^ses, viz.— (1st) I^X'LSOR.s, (2d) canines or cuspids,
(3d) PiiE^roLARS or bicuspids, and (4th) molars (Fig. 6). Tliis is
expressed by the dental formula as follows :
,. 2-2
2—2 1— 1 ,01. — 3 — 3
2—2' , c. 1 — 1' 2—2' , m. 3 — 3

(1) The incisors are eight in number, four above and four below,
two on each side of the median line. The two next to the median line
are called the central inckors, the ones next to them distally, the lat-
eral incisors.
(2) The canines arc four in number, two above and two below,
one on each side immediately approximating the lateral incisor on the
distal side.
(3) The bicuspids are eight in number, four above and four below,
—two on each side approximating the canines on the distal side.
The first of these next the canine is called the first blcusjyid, the one
next to it on the distal side the second bicuspid. The same designa-
tion applies to both upper and lower bicuspids.
(4) The molars are twelve in number, three on each side of each
jaw, approximating the second bicuspid on the distal side. The
molar next to the second bicuspid, both above and below, is called the
first molar ; the next one distally is called the second molar ; the next
one distally, and the last tooth in the jaw, is called the third molar or
" wisdom tooth " {dens sapiential).
Functionally, the incisors are formed for cutting, as their name im-
plies ; the canines for prehension and tearing (for which purpose this
tooth in lower animal forms is often excessively developed). It also
serves in guiding the bite. The bicuspids are the crushing teeth, and
the molars are formed for grinding, triturating and insalivating the
food.
The Incisors.
7. The Upper Central Incisor.—This is the first tooth in the den-
tal series in man. It is situated in the front of the mouth, next to the
centre of the arch, which is the mesial border of the intermaxillary
bone. In adult man these bones fuse with the anterior borders of the
right and left superior maxillary bones. Their junction with each other
marks the centre of the dental arch.
The general form is that of a truncated cone with its top flattened
out to form the cutting edge.
Its function is to cut or incise food, hence its name from the Lat.
incisus, " to cut into."