DENTAL INDICATIONS OP THE AGE OF A HORSE. 21? 
the dividers or second teeth at one year, and from the 
corner or inner incisors varying from fifteen months to two 
years. 
By this time the marks of the upper nippers have become 
almost entirely obliterated, so that at two years old the 
cavities in all the teeth have disappeared, as well of the 
lower as of the upper jaw. 
At this period the crowns of the nippers become insen¬ 
sibly smaller, and with their base necked. They also 
assume a yellowish-brown aspect, soon after which they 
loosen and almost entirely lose their attachment in the 
gums, and finally fall out. It is at this time the second 
period in the age of a horse commences. 
The mark in the tooth is occasioned by the food blacken¬ 
ing the hollow pit which is formed on their surface by the 
bending in of the enamel, which passes over the surface 
of the teeth; and by the gradual wearing down of the 
enamel from friction, and the consequent disappearance of 
it, we are enabled for several years to judge of the age 
of the animal. 
In the third year, the tushes sometimes begin to make their 
appearance, although there are instances of their not being 
developed until the fifth or sixth year. But the most general 
time for their appearing is in the fourth year. Little 
dependence can, therefore, be placed on them in determin¬ 
ing the age of the horse. We have given a representation 
of a three-year-old mouth, (fig. 5,) in which it will be seen 
the central teeth are larger than the others, and are pro¬ 
vided with two grooves in the outer convex surface. The 
mark is long, narrow, deep, and black ; and these teeth, not 
having attained their full growth, are somewhat lower than 
the others. In the two next teeth the mark is nearly worn 
out, and in the comer teeth it is slowly disappearing. 
