THE MOUTH. 25 



and in the form of the tooth at each surface as the 

 teeth wear clown through age and use, from a broad 

 ovoid form to a narrower triangular form ; and, as 

 a consequence, in the very aged horse the teeth do 

 not present a compact mass when viewed from the 

 front, but are more like so many pegs with spaces 

 between them. 



Lastly, on separating the lips of a horse in his 

 prime, and viewing the closed teeth from the side, 

 we see the large bold curve, as in Fig. 4, F; but 

 as age advances and the teeth w^ear away, 

 we get successsively, but of course gradually, 

 the curve G, then in extreme old age the angular 

 curve H. 



21.— We saw that with the milk teeth the central 

 nippers came first, then the two next them— one on 

 either side— and finally the two corner milk nippers, 

 and at nine months old to a year at most the foal 

 had a ' full mouth ' of nippers. First come, first 

 wear out; therefore the two central milk nippers 

 are shed at two and a half years ; the ones next 

 these are shed at three and a half, the corner nippers 

 at four and a half. So that at five years old — that 

 is giving the corner teeth six months to grow 

 up to having at least a cutting if not a grinding 

 surface— the horse is said to have a full mouth. 



Note. — The permanent teeth push out the tem- 

 porary ones, in order to gain the situation for them- 

 selves. If the work of pushing out is done for 



