260 



THE HORSE 



radically changed. Turn to Fig. 74, and note the cross- 

 section of a front incisor tooth when it has been in 

 wear five years, that is, when the horse is eight years 

 old, as compared with the teeth of a five-year-old 

 horse. At eight years of age there are indications that 

 the bones of the jaw and the teeth have already ceased 

 to enlarge. In some cases they show a slight shrinkage 



and the contour of the lower 

 jaw has become less rounded. 

 Compare Fig. 73 with Fig. 

 05. Finding that the cups 

 have nearly or quite dis- 

 appeared from the lower jaw, 

 we proceed to examine the 

 upper nippers. It is not 

 easy to get a clear view of 

 the upper nipper teeth of a 

 restless animal. If the horse 

 is eight years old the cups 

 will still be present in the 

 upper center nippers, but 

 they will not be deep. If the 

 teeth be viewed from the 

 side, Fig. 75, they will appear somewhat long, and will 

 meet at a sharper angle than they did when the horse 

 was but four years old. As the years go by, the angle 

 of the teeth increases. At four years of age, the upper 

 and lower teeth meet nearly vertically with each other, 

 at twenty at an angle of nearly forty -five degrees. 

 The tusks are becoming constantly larger, rounder and 

 blunter as the years advance. Compare Fig. 75 with 



4 years 



9 years 



14 years 



20 years 



FIG. 74. Cross section of an incisor 

 tooth, showing how the shape 

 changes with advancing years. 



