THE TEETH. 321 
though showing the mark very plainly, bear evidence of having been used. 
The tush is much grown, with its outer surface regularly convex, and its 
inner concave, the edges being sharp and well defined. The sixth molar 
is atits full growth, and the third is shed to make room for the permanent 
tooth in its place. These two last-named teeth should always be examined 
in cases where there is any doubt about the age. After five years, no further 
shedding occurs in any of the teeth. 
Fic. 9.—LowWeEk NIPPERS AND TusHES aT Five YEARS OLD. 
1. 1, Central nippers, with their marks almost 3. 3. Corner nippers, with the mark plainly 
entirely worn out. seen, but the edges partially worn. 
2. 2. Next nippers, showing marks partially 4. 4. Tushes, with the groves inside almost 
worn. obliterated. 
THE SIX-YEAR-OLD MOUTH is the last upon which any great reliance can be 
placed, if itis desired to ascertain the age of the horse to anicety,; but by 
attentively studying both jaws, a near approximation to the truth may be 
arrived at. It is ascertained that the nippers of the upper jaw take about 
two years longer to wear out than those of the lower; so that until the 
horse is eight years old, his age may be ascertained by referring to them, 
nearly as well as by the lower nippers at six. But as different horses 
wear out their teeth with varying rapidity, it is found that this test cannot 
be implicitly relied on; and in crib-biters or wind-suckers the upper teeth 
wear out wonderfully soon. Fig. 10 is taken from the lower jaw of a six- 
year-old horse, showing the marks of the central nippers almost obliterated, 
but still presenting concentric circles, of discoloured brown tartar in the 
middie ; next to which is the cement, then the enamel, and the dentine, 
with a thin layer of enamel outside. Up to this age, the nippers stand 
nearly perpendicular to each other, the two sets presenting a slight con- 
vexity when viewed together, as seen in fig. 2, page 372. Afterwards 
Y 
