140 THE STRUCTURE OF THE HORSE. 



twenty-four teeth, three incisors and three molars 

 above and below on each side of each jaw. The 

 upper teeth, as a rule, appear somewhat earlier than 

 those of the lower jaw. Within a very few days 

 after birth the central incisors make their appearance, 

 and by the end of the second week they are fairly 

 up in the mouth. The first and second molars come 

 into place about the same time. Between the first 

 and second month the second (lateral) incisors ap- 

 pear, then the third molar, and finally (at about 

 nine months) the third (corner) incisors, which com- 

 plete the milk dentition. Of the permanent teeth, 

 the first true molar appears about the end of the first 

 year, followed by the second molar before the end of 

 the second year. These teeth are thus in place be- 

 fore any of the milk-teeth have been shed. At about 

 two and a half years the first premolar replaces its 

 predecessor. Between two and a half and three 

 years the first permanent incisor appears. At three 

 years the second and third premolars and the third 

 true molar have appeared, at from three and a half 

 to four years the second incisor, at four to four and 

 a half years the canine, and finally, at five years, 

 the third (corner) incisor, completing the permanent 

 dentition. Up to this period the age of the horse is 

 clearly shown by the condition of its dentition, and 

 for some years longer indications can be obtained 



