FUNDAMENTAL CONSIDERATIONS 



107 



This occurs when the animal is two and one-half to three 

 years of age, the remainder of the temporary teeth being 

 replaced as described subsequently. 



Order of Appearance of Incisors. — The permanent incisors 

 of both the upper and lower jaws appear at the same time, 

 and in determining the age during this stage of dentition 

 reference should be made to the teeth in both jaws. The 

 horse has six permanent incisors in each jaw in a full mouth 

 and these appear as follows : 



Fig. 28. — Lower incisor and 

 canine teeth of horse, five years 

 old: 7', 72, /', incisors; C, canine. 

 (Courtesy of L. W. Sisson, from 

 Anatomy of Domestic Animals.) 



Fig. 29. — Upper incisor and 

 canine teeth of horse five years old : 

 7', 7^, 7^, incisors; C, canine. 

 (Courtesy of L. W. Sisson, from 

 Anatomy of Domestic Animals.) 



The center pair of incisors appear first, displacing the 

 temporary pair when the animal is two and one-half to three 

 years old. The second or intermediate pair displace the tem- 

 porary teeth when the animal is three and one-half to four 

 years old, and the third or corner pair displaces the corner 

 temporary incisors at four and one-half to five years old. 

 When these permanent incisors are all completely up and in 

 wear the horse has a full mouth. After the animal reaches 

 this five-year stage, the age is determined by the order of 

 disappearance of the cups in the incisors. 



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