222 
MANUAL OF MODERN FARRIERY 
upper incisors are less liable to friction and wear than those 
of the under jaw, in consequence of the lower jaw alone 
being moved in the act of chewing, and the upper jaw 
being fixed and without motion : its office is only to resist 
the pressure of the under jaw in eating. 
The tushes are of no use whatever in enabling us to 
determine the age of a horse, because the change of their 
form is very uncertain. They will sometimes be blunt at 
one year, and in other cases will remain pointed to eighteen 
or even twenty. They do not rub against each other like 
the teeth, and are consequently less liable to be worn down. 
After eight, we are best enabled to judge of the age of 
a horse from the form of the upper surface of the incisors. 
At this time all of them are transversely oval, that is, the 
length of the oval extended from one tooth to another. As 
the animal advances in years, they diminish in size, the 
width being the first affected, and not their thickness, 
They soon grow a little apart from each other, and their 
surface rounded, which continues to be the case up to 
thirteen years ; after this they assume a new character, and 
become triangular in the same order in which they had 
become oval and rounded. 
At nine, the nippers or middle incisors are rounded, and 
the next teeth or dividers begin to assume that form ; the 
remainder of the funnel of these four teeth is round, and 
quite close to the inner edge of the tooth ; they also ex¬ 
hibit the septum of the root. 
At ten, the incisors will be considerably shortened in 
their oval form. There is merely a rudiment of the funnel 
of the nippers, as well as in the dividers, and the remainder 
of the central enamel touches the inner edge of the table of 
the tooth. The nippers and dividers are rounded, and the 
corner teeth exhibit an oval form. (Plate v. fig. 3.) 
