380 STRUCTURE OF THE TEETH, 



commonly supposed to be filled up ; but In fact disappears by 

 the borders of the cavity being worn down. It takes about three 

 years to wear the teeth down to the bottom of these cavities ; 

 thus, the anterior teeth, being first formed, are first to lose their 

 mark ; the middle teeth following the next, and the corner teeth 

 the succeeding year. The French distinguish the incisor teeth 

 by calling the anterior ones the nippers, the corner the corners, 

 and those between them the dividers ; which terms will serve to 

 distinguish them in this place. When the incisors first appear, 

 the anterior border of the cavity is somewhat higher than the 

 posterior internal border ; but in the course of a year it is worn 

 down level. 



For many years it has been customary to judge of the age by 

 the marks we have mentioned ; but at eight years old, the horse 

 is said to be aged ; and after this time it was considered to be 

 impossible to ascertain the age. There are, however, other 

 means which enable us pretty generally to judge of the age, if 

 not with certainty, at any rate approaching to it. If we take an 

 incisor tooth and make three or lour transverse sections of it, we 

 shall find that each surface is of a different shape. The tooth 

 becomes gradually less from side to side, and more from front to 

 rear. At a certain depth it becomes triangular, and, lower still, 

 the oval appears almost reversed, the diameter being less from 

 side to side than from front to rear. (See fig. 13., a, b, c, d, e.) 

 Each of these several portions of the tooth becomes, in the 

 course of time, its face, the shape of which therefore enables us 

 to approximate to the age. This is still more assisted, up to a 

 certain age, by the fact that the enamel that forms the side of 

 the infundibulum dips deeper into the tooth than the cavity 

 within it. It may therefore be seen in the centre of the face for 

 some years after the disappearance of the mark.* 



In this countiy, for years past, it has been customary to reckon 

 the ages of horses from the 1st of i\Iay, although they may, in 

 many instances, be foaled several months either before or after 

 this date. It has, however, within these few years, been de- 

 cided by the jockey club that the ages of race horses shall be 

 reckoned from the 1st of January. They are generally foaled 

 earlier than other horses, it being desirable that they should be 

 as early in the year as possible, in consequence of the practice of 

 running horses so early as two and three years old. 



A few months, in a young animal, often makes a material 



* The funnels in the upper incisor teeth being deeper, and the wear being 

 less than in the under teeth, the marks are longer disappearing. It has been 

 stated that there are two years' space between the disappearance of the marks 

 in the diiferent teeth ; the mithlle teeth losing them at ten, the dividers at 

 twelve, and the corners at iburteen ; but this is a matter of much irregularity 

 and uncertainty. Their presence and disappearance will, however, serve to 

 assist the other signs in informing us of the age. — Ed. 



