56 



The Diseases of Animals 



Fig. 21. Horse's teeth at eight years of age 



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 

 broad from side to 



side, and approach the perpendicular with reference 

 to the jaw. As the horse gets older, the incisors wear 

 down, becoming nai-rower from side to side and 

 wider from before back, so that the upper surface of 



Fig. 22. Horse's teeth at ten years of age 



