DENTAL INDICATIONS OF THE AGE OF A HORSE. 215 



which the different layers are united, and which fill tho 

 spaces between the columns, soon begin to wear awa}^, while 

 the enamel remains, thus occasioning the uneven surface 

 presented by them, and which is the very best structure 

 for them to possess in order to grind down the food. 



The grinders in the lower jaw, as we have above observed, 

 having been only provided with four of those bags, are con- 

 sequently smaller and narrower, and more regular in their 

 form than the upper ones. They are placed horizontally in 

 both jaAvs ; but in the lower one the higher side is within, 

 and gradually shelving outwards, while in the upper jaw 

 the higher side is without, and shelving inwards ; by which 

 beautiful arrangement the triturating or grinding motion is 

 most advantageously performed. Each of the grinders is 

 different in structure and appearance, and . can be respec- 

 tively recognised with the situation of, and the jaws to 

 which they belonged. 



When the foal is born, it has the first and second 

 grinders, which are large compared with the size of those 

 by which they are afterwards replaced. In six or eight 

 days after birth, the centre nippers make their appearance. 

 These are large in comparison to the size of the jaw, and 

 occupy its whole front, as represented in plate iv. fig. 1. 

 In three weeks or a month the third grinders will have 

 made their appearance, and within six weeks an additional 

 incisor on each side of the two first, both above and below, 

 will be visible, and soon after completed, and the jaw will 

 have assumed the form exhibited in fig. 2. The two molars 

 that the foal has at birth remain until the animal is two 

 and a half years of age, at which time they are forced out of 

 their sockets by the protrusion of the second set, or re- 

 placers. But from this time there is no use in consulting 

 the grinders for the age of the horse, as the best tests and 



