of the Animals of the Farm. 
411 
From eight to ten years old the changes occasioned by the 
•wear to which the teeth have been subjected are not sufficiently 
regular to enable the examiner to speak positively as to the 
exact age, but during this period the cavity in each lower 
central incisor is worn out, and only a small circle of enamel 
in the tables of the central incisors remains to indicate its 
position. In the corner teeth at ten years old the central 
enamel has become round, or nearly so, as shown in the ac- 
companying drawing (Fig. 18) of the mouth of " Solace," a 
steeplechase mare, foaled in 1842. I'he teeth are depicted 
exactly as they appeared in the summer of 1852, and fairly 
represent the characters of the ten-year-old mouth. 
Fig. 18. — Incisors of Horse, (^^' Solace") at ten years. 
At twelve years old the teeth are longer from the receding 
of the gums, and are also narrower in consequence of having 
been worn towards the fang, which decreases in width from the 
neck of the tooth to its termination. The tusks are blunted, 
especially those of the upper jaw, and a quantity of tartar 
often surrounds those in the lower jaw. The incisors at this 
