of the Animals of the Farm. 23 



of the fifth year, only the anterior edge exhibiting the effects 

 of attrition. The tables of the lateral incisors are fully formed 

 by the central cavity being surrounded by a line of worn surface. 

 In the central incisors the cavity has become extremely shallow. 

 The development of the corner permanent incisors completes 

 the permanent dentition of the horse. 



Indications of Age of the Horse afforded by the Teeth 

 after the completion of permanent dentition. 



The horse occupies an exceptional position among the 

 animals of the farm in respect to the evidence of age which is 

 afforded by the teeth after all the permanent organs are deve- 

 loped, and there is no longer anything to be gained by a com- 

 parison between them and the temporary. All animals exhibit 

 distinct signs of wear in their teeth as age advances ; but. owing 

 to the peculiar arrangement of the structures of which the teeth 

 are formed, the horse alone gives definite evidence which can be 

 interpreted by a careful observer up to an advanced period of 

 the animal's life. 



It was explained in the preliminary observations on the teeth 

 of the horse that the permanent incisors present two somewhat 

 oval surfaces, one at the upper part of the tooth and the other 

 at the end of the fang : the long axis of the first being hori- 

 zontal, and that of the second vertical ; and, as a consequence, 

 the wear of the tooth, from the upper towards the lower oval, 

 results in a series of figures, some of which are depicted on 

 page 7. 



' After five years, evidence of age is to be obtained by the 

 inspection of the tables of the incisor teeth, in regard to their 

 form, the extent and depth of the central cavity, and the form 

 of the central enamel. 



At six years old the horse's age is judged chiefly by the 

 amount of wear which the corner teeth have sustained, although 

 there are other marks that are worthy of notice. 



The corner teeth have lost their shell-like character, and a 

 line of worn surface surrounds the central cavity, excepting a 

 small point where the corners touch the lateral incisors. The 

 line of wear is broader at the anterior than at the posterior edge, 

 and the cavity is still of considerable depth. 



In the lateral incisors the cavity (or mark) is shallow, and 

 much smaller than that of the corner incisors. The figure 

 described by the central enamel is approaching an oval. The 

 cavity in the central incisor is almost worn out, but its bound- 



