762 EXAMINATION FOE AGE. 



variation. Hence, it is not at all uncommon to meet with mouths, 

 the " marks " in which indicate that the animal is " younger " 

 than he really is ; that he is " younger '' on one side of his mouth 

 than on tlie other ; or that one or more teeth retain these cavities 

 to an unusually late period. The varying hardness of the teeth 

 and of the forage, naturally contribute to irregularity in the 

 amount of wear. In less frequent cases, the marks disappear 

 earlier than usual. It is not a very rare occurrence to observe 

 that the mark has disappeared out of the lateral lower incisors in 

 a six-year-old animal. These considerations render the " mark,'' 

 of itself, anything but a safe guide to the determination of a horse's 

 age. The roundness of the tables of the lower central incisors, 

 and, to a less degree, of the lateral ones ; the oval appearance of 

 the tables of the corner incisors ; the shortness and central position 

 of the dental star ; the smallness of the central enamel of the 

 lower central teeth, and its closeness to the posterior edge of the 

 table ; the obliquity of the teeth, as viewed in profile ; and the 

 flatness of the curves of the incisor teeth will afford unerring 

 proofs that the animal ought to be " beyond mark of mouth," 

 namely, over eight years. 



Retention, for an unduly long period, of the apex of the cone 

 of the central enamel of the permanent incisors, gives a false 

 appearance of comparative youth to the mouths of some horses. 

 This, of course, occurs only after the cavity (or " mark '') has dis- 

 appeared; and is due to the fact of the solid apex of the cone of 

 enamel being deeper than usual ; to the hardness of the teeth 

 themselves ; or^ to some extent, to the soft nature of the food. 

 The form and degree of obliquity of the incisors, and the position 

 and extent of the dental star, will serve as guides from which to 

 draw correct deductions as to the age. 



Irregularity in the Respective Size of the Upper 

 and Lower Jaw. 



The chief irregularity under this heading, is that of " parrot- 

 mouth," in which the teeth of the upper jaw project, to a con- 

 siderable extent, beyond those of the lower jaw (post-normal 

 occlusion of dentists) (Figs. 207, 208, and 209, pp. 764 and 765). 

 Although parrot-mouth in a fully developed form, appears as a 

 rule only in old horses ; we may commonly see, even in five and 

 six year olds, the upper central incisors projecting a little beyond 

 the lower ones. This tendency is slightly shown in Fig. 2f7 

 (p. 795) ; and in a well-marked manner in Fig. 261 (p. 804). It 

 is almost certain that animals possessing this peculiarity would 



