THE TEETH 31 



At four years and six months the corner permanent incisors are cut, 

 and when these teeth are well up, and the inner and outer edges ot 

 their tables are level, the horse h Jive years old. 



The last two permanent molars (numbers three and six in position) in 

 each jaw are cut between the ages of four and five. 



At six the corner incisors are exhibiting evidence of wear. The 

 infundibula of the two middle incisors may have entirely disappeared. 

 This disappearance was formerly looked upon as constant at this age, 

 but for the reasons before stated such is not the case, and some trace ot 

 them is frequently found to remain, although the depressions are much 

 more shallow than are those in the lateral or corner incisors. At this 

 age also a new feature presents itself on the tabular surface of the 

 central incisors in the form of a blackish or brownish line which runs 

 transversely between the disappearing infundibulum and the anterior 

 edge of the tooth. This is the first appearance of what is known as the 

 dental star, and it indicates the fact that so much of the tooth has been 

 worn away as to bring the upper extremity of the pulp cavity filled 

 with dentine into appearance on the table. 



A similar change occurs in the infundibula of the lateral incisors at 

 the age of seven, the infundibula being either missing or much more 

 shallow, and at this age the dental star appears in these teeth. The first 

 appearance of the dental star is not noticeable excepting under careful 

 observation. When the horse is seven years old it is much better marked 

 in the central incisors, and at eight there should be no difficulty in 

 seeing it. 



Its position also seems to change between the years of six and eight. 

 At first it is, as already stated, quite close to the anterior edge of the 

 tooth, but as the animal advances in age the star recedes from the edge 

 and approaches nearer the centre of the table. 



From the age of eight onwards very little definite evidence can be 

 obtained, but still certain further changes occur which assist in arriving 

 at an approximate estimate. 



