io;8 



THE UNGULATES, OR HOOFED MAMMALS 



the centre of the crown is occupied by a pit surrounded with a ring of enamel, this 

 being technically known as the "mark." In the figures, A shows the jaw of a very 

 young colt, with only the first and second milk-incisors protruded, both being un- 

 worn; the third milk-incisor would appear later. In B, which indicates a horse 

 about three years old, the first permanent incisor has just appeared, after pushing 

 out the corresponding milk-tooth. Between three and one-half and four years, the sec- 

 ond permanent incisor would have likewise appeared, and about half a year later 

 the tusk protrudes from the gum. At five years, the third incisor would have dis- 

 placed its predecessor, and the dentition would then be complete. This state is 

 shown at C, which represents the jaw of a six-year-old horse, in which the third in- 

 cisor is partly worn, although still retaining a large mark. Up to five years, the age 

 of a horse can consequently be determined with accuracy, and also approximately 



THE UPPER INCISOR AND CANINE TEETH OF THE HORSE AT VARIOUS AGES. 

 (A. at 30 days; B. at 3 years; C. at 6 years; D. at 8 years; E. at 15 years; F. at 30 years.) 



for some years longer. As a rule, the mark disappears in the first incisor of the 

 lower jaw at six years, in the second at seven, and in the third at eight, while in 

 the corresponding upper teeth it persists about two years longer. D shows the up- 

 per jaw of a horse about eight years of age, when the mark has nearly disappeared 

 in the first incisor. After the mark has been lost in all the incisors no indications 

 of age are afforded. In old horses, as in E, a kind of spurious mark is, however, 

 produced, owing to the tooth having become so much worn down that the pulp 

 cavity of its basal portion is exposed. Such spurious marks have, however, no ring 

 of enamel, and cannot be made to counterfeit the true mark, although attempts to 

 make them pass for this were, and perhaps still are, made by unscrupulous dealers. 

 When the spurious mark makes its appearance, the section of each incisor forms a 

 Wide triangle, the broad and flattened crown having been completely worn away; 



