5G THE PERMANENT DENTITION. 



lows between the fourteenth and twentieth months. 

 The crowns of the premolars and the last true molar 

 are now advancing in the closed sockets of reserve. 

 The first premolar displaces the second,* and usually 

 at the same time the very small deciduous molar, at 

 from two years to two years and a half old. The first 

 permanent incisor rises above the gum between two 

 years and a half and three years. At the same period 

 the second premolar pushes out the third deciduous 

 molar. The last premolar displaces the last deciduous 

 molar about the completion of the fourth year, and 

 the appearance above the gum of the last true molar 

 is usually anterior to this. The second incisor pushes 

 out its predecessor between three and a half and four 

 years. The small persistent canine or tusk, contrary 

 to the usual rule, next follows, its development having 

 received no check by the retention of its rudimental 

 predecessor. Its appearance indicates the age of four 

 years ; but it sometimes appears earlier, rarely later. 

 The third incisor pushes out the deciduous one about 

 the fifth year, but is seldom completely in place before 

 the horse is five years and a half old. The third pre- 

 molars are then usually on a level with the other 

 grinders." 



On the completion of the fifth year a male foal is 

 called a horse, a female or filly foal a mare. The teeth, 

 however, are not all fully developed before the sixth 

 year, and the roots of the grinders do not begin to 



* To prevent confusion, it should be understood that Prof. 

 Owen calls the "very small deciduous molar" here referred to 

 the first deciduous molar, notwithstanding it is not functionally 

 developed. Hence, as it has no successor, the first premolar dis- 

 places the secortd deciduous molar, the second premolar the thircl 

 deciduous molar, and the third the fourth. 



