EXAMINATION OF TflE MOUTH FOK AGE. 



87 



Ly Fig. 10 and by the plates giving the different ages. 

 As a rule, the tushes become shorter with age ; although 

 we sometimes find them very long, and even with their 

 rearmost edge sharp, in old horses. I cannot satis- 

 factorily explain how it is that these teeth usually wear 

 down so fast. Apparently, they are subjected to only a 

 slight amount of friction. 



Fig. 17. — The arches of the incisor teeth exposed, to show tlieir 

 progressively increasing obliquity. 



4. The permanent incisors grow more and more 



oblique (see Figs. 16 and 17), owing to their shape, and 



position in the jaws. Their crowns increase in length, 



on account of their wear not keeping pace with the rate 



at which the tooth is pushed out of its socket. 



