10 Feb., 1919.] Ageing of Horses. 97 



AGEING OF HORSES. 



By R. W. Johnstone, B.V.Sc. Veterinary Inspector. 



The age of a horse can be told with some degree of certainty by the 

 appearance of its front or incisor teeth. Two complete sets of these 

 appear, viz., temporary milk or foal teeth and then the permanent or 

 horse teeth. There are six incisors in each jaw in both the temporary 

 and permanent sets, and they are spoken of as central, lateral, and 

 comer teeth on each side of the mouth. In the male a tusk appears in 

 the space between the incisors and molars when the animal reaches 

 maturity, i.e., when he is five years old. All horses have six molars or 

 back teeth on each side of both the upper and lower jaws; the first, 

 second, and third are both temporary and permanent ; the- fourth, fifth, 

 and sixth permanent only. 



Temporary incisors are small, white, and have a distinct neck and a 

 short fang or root which practically disappears as the permanent teeth 

 develop underneath. Permanent incisors differ in that they are 

 broader and browner and have no distinct neck, while the fang or root is 

 long and strong. 



For the purposes of description, incisor teeth may be divided into 

 the following parts : — 



(1) The table or wearing surface. — 'The part which bites the food 

 or meets its fellow on the opposite jaw. 



(2) The mark. — A depression in or near the centre of the table. 

 The inner surface, which is blackened by contact with food, is lined 

 with enamel, which stands up on the surface as a distinct, easily 

 felt ring. In the new tooth the mark is broad and deep, but with 

 age and wear it becomes shallower and narrower, and finally dis- 

 appears altogether. 



(3) The neck is where the tooth enters the gum. 



(4) The crown is that portion of the tooth above the gum. 



(5) The fang is that part within the jaw. It is hollow, and its 

 cavity — the fang hole — contains nerves and blood vessels which 

 sensitize and nourish the tooth. As the tooth grows up, the fang 

 hole becomes filled with calcareous material, which is lighter in 

 colour than the surrounding portions of the tooth, and when the 

 tooth wears to the level originally occupied by the fang hole, the 

 calcareous material appears as a white line in front of the mark on 

 the table of the tooth. 



Horses teeth differ from those of most other animals in that they 

 continue to grow and wear away throughout life. This continual 

 growth and wear cause the variations which enable us to arrive at the 

 animal's approximate age. 



At birth a foal has two central temporary incisor teeth in each jaw. 



At about two months the lateral temporary incisors are cut. 



At from six to eight months the corner temporary incisors are cut. 



At one year the whole of the temporary incisors are in wear — the 

 corners on the front edge only. 



At two years and six months the central permanent incisors are cut. 

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