488 TEETH OF THE HORSE. 



appearance of the incisors. At six years is perhaps the best by 

 which the horse's age can be certainly and precisely told; though 

 by careful observation, one may come very near the truth some 

 years later. At this age (six years), it is the lower jaw that we 

 must study, as shown in Fig. 4' 



This cut shows the marks in the central nippers almost worn 

 out, but still looking like surrounding circles of brown matter in 

 the middle ; next to this appears the cement, then the enamel, then 

 the dentine, with a thin layer of enamel outside. Up to this time 

 the nippers are nearly perpendicular to each other, only a slight 

 convexity being apparent where they are seen together. 



Figure 5. 



Upper Nippers of Eight- Years-Old. 



An appearance, similar to that already shown in the lower nip- 

 pers at six years of age, will be observed in the upper nippers at 

 eight. This will appear in the cut Fig. 5. 



The upper middle nippers are quite worn down at nine years 

 of age, the next pair have only a small mark left on their level sur- 

 face, and the corner ones have only a black stain, without any notice- 

 able sinking in the middle. 



After a horse is nine years of age, you can only approximate 

 his age from the teeth. They grow in length slowly, and are 

 nearer in a line with the jaw. The surface of the nippers, as seen 

 by the eye, assumes a triangular shape, in place of the oval appear- 

 ance shown in Fig. 5, and this shape again disappears after twelve 

 years of age, the tooth becoming almost round. As the length of 

 the tooth increases, the color is changed until, in the oldest 



