DENTITION OF HORSES. 415 



of worn surface. In the central incisors the cavity has be- 

 come extremely shallow. 



With the development of the permanent incisors the per- 

 manent dentition of the horse is completed. 



From the completion of permanent dentition the evidence 

 of age. is to be obtained by the inspection of the tables of 

 the incisor teeth in regard to their form, the extent and 

 depth of the central cavity and the shape of the central 

 enamel. 



At six years old the horse's age is judged chiefly by the 

 amount of wear which the corner teeth have sustained, 

 although there are other marks which are worthy of notice. 

 The corner teeth have lost their shell-like character, and a 

 line of worn surface surrounds the central cavity, excepting 

 a small point where the corners touch the lateral incisors. 

 The line of wear is broader at the anterior than at the poste- 

 rior edge, and the cavity is still of considerable depth. In 

 the lateral incisors the cavity (or mark) is shallow and much 

 smaller than that of the corner incisors. The figure de- 

 scribed by the central enamel is approaching an oval. The 

 cavity in the central incisor is almost worn out but its boun- 

 daries are distinctly marked by the central enamel which 

 surrounds it, forming an elliptical figure which extends 

 almost across the tooth in the direction of its long diameter, 

 and is nearer to the posterior than to the anterior edge. 



The tusks are usually well developed, but their points are 

 not worn, and the hollows on their inner surfaces are well 

 defined. 



All these characters are shown in Fig. 11 of the lower 

 incisors of a six-year-old horse. 



At seven years old the tables of the corner teeth are per- 

 fectly formed and the cavity in each tooth is very shallow. 

 The central enamel, however, is well defined and forms an 

 elliptical figure, which is nearer to the posterior than to the 

 anterior edge of the tooth. In the lateral incisors the central 

 enamel forms a figure which is nearer to the oval than to the 

 elliptical, and the mark, which is very shallow, does not ex- 

 tend so far across the table of the tooth as it does at six years 



