THE TEETH. 259 



smaller in size than the permanent teeth and somewhat different 

 in shape. They are more rounded in front, and hollow towards 

 the mouth, the outer edge being at first much higfrer than the 

 inner. As they wear down, these two edges soon become level, 

 but the corner nippers maintain this appearance for a long time. 

 At six months the central nippers are almost level, with the black 

 "mark" in their middle wide and faint; and about the ninth 

 month the next nipper on each side above and below is also worn 

 down almost to a level surface. 



DURING THE SECOND YEAR the following changes take place : 

 In the first month, and sometimes towards the end of the first 

 year, a fourth grinder is cut all round, which commences the set 

 of permanent teeth, the three first molars only being shed. At a 

 year and a half, the mark in the central nippers is much worn out, 

 and has become very faint; the second is also worn flat, but is not 

 so faint; and the corner nippers are flat, but present the mark 

 clearly enough. In colts which have been reared on corn and 

 much hay, the wearing down proceeds more rapidly than in those 

 fed upon grass alone. 



THE THIRD YEAR is occupied by the commencement of the 

 se.cond dentition, which is effected in the same order in which the 



FlQ. 3. THREE-YEAR-OLD MOUTH. 



B. Anterior maxillary bone. 3. 3. Corner milk teeth, still showing ceo- 



1. 1 Central permanent nippers, nearly tral mark. 



full-grown. 4. 4. Tushes concealed within tho jaw. 



2. 2. Milk teeth worn down. 



milk teeth made their appearance. Both sets are contained within 

 the jaw at birth, the permanent teeth being small and only par- 



