350 OUR HUMBLE HELPERS 



other when the animal chews its forage, the edge of 

 the enamel first crumbles, then wears off little by 

 little, and finally disappears altogether, leaving the 

 ivory exposed on the top of the crown. This fric- 

 tion always going on, the coronal cavity or pit be- 

 comes less and less deep until at last there is noth- 

 ing of it left. The upper face of the crown is then 

 flat instead of hollowed-out as it was at first. This 

 gradual obliteration of the hollow or pit in the crown 

 of the incisor, whether in the first or in the second 

 set of teeth, furnishes a means of determining the 

 horse's age. I have just told you when the milk 

 teeth make their appearance; I will now add what 

 is to be said about their wearing down. The cen- 

 tral incisors of the first set of teeth are worn down 

 so that their crowns are flat in ten months, the sec- 

 ond incisors in one year, and the third incisors in 

 from fifteen months to two years. Let us next con- 

 sider how the horse's age may be determined at a 

 later period. 



"I here show you a picture of the incisors of the 

 lower jaw. What do you see that will help you to 

 estimate the horse's age?" 



"I see in the first place," answered Jules, "that 

 the teeth are not all of the same age. The two in 

 the middle, the central incisors as you call them, are 

 newer, since the cavities in their crowns are in good 

 condition, with their sharp edges of enamel. The 

 others are older; their crowns are blunted by fric- 

 tion; in fact, they are a good deal worn down." 



"Are all six of the same cutting?" 



