THE TEETH 



361 



placed, if it is desired to ascertain the age of the horse to a nicety ; but by 

 attentively studying both jaws, a near approximation to the truth may be 

 arrived at. It is ascertained that the nippers of the upper jaw take about 

 two years longer to wear out than those of the lower ; so that until the 

 horse is eight years old, his age may be ascertained by referring to them, 

 nearly as well as by the lower nippers at six. But as different hoi^ses wear 

 out their teeth with varying rapidity, it is found that this test cannot be 

 implicitly relied on ; and in crib-biters or wind-suckers the upper teeth 



I'ia. 8.— rpPER Nippers and Tushes at Five Teae=; Oijj 



Comer nipj 

 "ishes wel 

 groove on the outside plainly, 



1. 1. Central nippers, with, the mark stiU un- 



obliterated. 



2, 2. Next nippers, with the mark still plainer. 



with the edges very sligutiy woru. 

 4. 4. Tushes TveU developed, and still showing the 



wear out wonderfully soon. Fig. 10 is taken from the lower jaw of a six- 

 year-old horse, showing the marks of the central nippers almost obliterated 

 but still presenting concentric circles of discoloured bro^vn tartar in the 

 middle ; next to which is the cement, then the enamel, and the dentine, 

 with a thin layer of enamel outside. Up to this age the nippers stand 

 nearly pei^pendicular to each other, the two sets presenting a slight convexity 

 when viewed together, as seen in Fig. 2, page 354. Afterwards the nippers 

 gradually extend themselves in a straight line from each jaw, and, in the 

 very old horse, form an acute angle between them. 



