4. How is the age of the animal determined between the fifth and ninth
years?

5. What changes in the appearance of the table surfaces occur between ten
and fifteen years of age?




CHAPTER XX

IRREGULARITIES OF THE TEETH


Parrot-mouth, Lantern-jaw and Scissor-mouth.--The common deformities of the
jaw and teeth are the overshot or parrot-mouth, the undershot or
lantern-jaw, and the scissor-mouth. These different deformities result in
unequal wear on the table surfaces of the incisors and molars. In both the
overshot and undershot jaws, the incisor teeth become abnormally long. In
the _parrot-mouth_, the wear occurs on the posterior face of the superior
and the anterior face of the inferior incisors, the teeth becoming worn to
rather a sharp edge, depending on the degree of the deformity. In the
_lantern-jaw_, the wear occurs on the posterior face of the lower and the
anterior face of the superior row of incisors, the teeth taking on somewhat
the same shape as the parrot-mouth. The greater the deformity and the older
the horse becomes, the more difficult it is for the animal to feed or
graze on pasture.

In all horses, the two rows of molar teeth are wider apart in the superior