112 



THE STRUCTURE OF THE .HORSE 



gradual maturation of the latter, and especially while 

 the jaws are acquiring size and strength sufficient to 

 support them. In all cases these teeth disappear (by 

 the absorption of their roots and shedding of the crowns) 

 before the frame of the animal has acquired complete 

 maturity. As the first set of teeth are, as a general rule, 

 present during the period in which the animal is 

 nourished by the milk of the mother, the name of 4 milk- 

 teeth ' (French, dents de lait ; German, Milchzdhne) has 

 been commonly accorded to them, although it must be 

 understood that the time of their duration has nothing 

 to do with that of lactation. ' Temporary teeth,' or ' de- 

 ciduous ' teeth, are, perhaps, therefore, better names. 

 No mammal has more than two sets of teeth. 



Special Characters of the Teeth of the Horse. — Incisors. 

 — To return to the teeth of the horse. The incisors, or 

 ' nippers,' as they are called in veterinary language, 

 of each jaw, are placed in close contact, forming a semi- 

 circle. The crowns are very large, somewhat chisel- 

 shaped, and of nearly equal size. They have all a 

 peculiarity not found in any other existing mammal, 1 

 and seen only in the Equidce of comparatively recent 

 geological formations. In the most primitive species 

 these teeth were simple, and chisel- or awl-shaped. 

 When their crowns became worn in consequence of 



1 Mac rauchcnia, an extinct South American Perissodactyle, had 

 somewhat similar incisors. 



