70 
COMPARATIVE ZOOLOGY. 
of enamel. In the Cats and Dogs, they are narrow and 
sharp, passing by each other like the blades of scissors, 
and therefore cutting, rather than grinding, the food. 
The more purely carnivorous the species, and the more 
it feeds upon living prey, the fewer the molars. In ani¬ 
mals living on mixed diet, as the Hog and Man, the 
crowns have blunt tubercles. Premolars, or bicuspids, 
are those which were preceded by milk-teeth; the true, 
or back, molars had no predecessors. 
The dentition of Mammals is expressed by a formula, 
which is a combination of initial letters and figures in 
Fig. 35.—Teeth of the right lower jaw of adult male Chimpanzee (Troglodytes niger ), 
natural size. The molar series does not form a curve, as in Man. 
fractional form, to show the number and kind of teeth 
on each side of both jaws. Thus, the formula for Man 
is: 
• 2 — 2 . ^ 
^ 2 - 2 ’ 
1—1 . 2 — 2 . 
5 1—1 5 V J 2 — 2 ’ 
m, §=£ = 32. 
The teeth of Mammals are always restricted to the 
margins of the jaws, and form a single row in each. But 
they rarely form an unbroken series. 28 The teeth im¬ 
planted in the premaxillary bone, and in the correspond¬ 
ing part of the lower jaw, whatever their number, are in¬ 
cisors. The first tooth behind the premaxillary, if sharp 
and projecting, is a canine. 
Each tooth has its particular bony socket. 29 The molars 
