56 The Diseases of Animals 
the cavity has largely disappeared at six years (Fig. 
19), the lateral at seven years (Fig. 20) and the corners 
at eight years of age (Fig. 21). The date-cavities in 
the incisors of the 
upper jaw do not dis- 
appear as regularly as 
the lower, and are less 
to be depended upon. 
In general, the date- 
cavities disappear 
from the central up- 
per incisors from nine to nine and a half years; from 
the lateral upper incisors from ten to ten and a half; 
and from the upper corner incisors from eleven to twelve 
years. Date-cavities sometimes persist in the upper 
incisors for a longer period, especially in horses that are 
stall-fed. In examining date-cavities, a careful com- 
parison with the preceding and succeeding years should 
always be made. After a date-cavity:is worn out, a 
small black spot called a “dental star” remains, and 
frequently a small 
cavity, which should 
not be mistaken for a 
date-cavity. 
In young horses, 
the incisor teeth are Fig. 22. Horse’s teeth at ten years of age 
broad from side to 
side, and approach the perpendicular with reference 
to the jaw. As the horse gets older, the incisors wear 
down, becoming narrower from side to side and 
wider from before back, so that the upper surface of 
Fig. 21. Horse's teeth at eight years of age 
