AGE, AS INDICATED BY THE TEETH. 



309 



A few months before five, the horse sheds the two remaining milk 

 teeth, which are replaced by permanent. Thus the jaw is now furnished 



Fig. U-i. 

 Teeth at Four Years. 



with six permanent incisors, but the corner teeth are mere shells, having 

 no internal wall. The absence of this wall distinguishes the five from 

 the six year old mouth (Figure 143). 



Fig. 143. 

 Teeth at Five Years. 



A few months before six, the inner wall of the corner teeth has 

 grown up level with the outer wall. (Figure 144). 



The mouth is now fully comj)lete in incisors, and no further struc- 

 tural changes take place in them. As a general rule, the upper tempo- 

 rary teeth fall out a little before those in the lower jaw. 



Up to six years old, therefore, inasmuch as we have structural changes 



