Of the age of a horse, after eight years, only those who have given much time and study to the subject can determine anything very accurately. The receding of the gums and wear and tear of the teeth, of course, are indubitable signs of age. The lower jaw, too, as a horse advances in years, tends to bend outward, making an angle more and more acute rather than an obtuse angle. The cross-sections of the teeth, too, are smaller as the teeth grow up from the gums to supply the parts worn away. Up to the age of six years the age of the horse can be determined fairly accurately, but even then difference in food and care make a marked difference in the wear on the teeth.
The young foal has two and sometimes three temporary molars in each jaw (Plate V.). When about twelve months old another molar appears (Plate V.) which is permanent, and before the completion of the second year a fifth molar, also permanent, appears (Plate V.). Between the age of three and four the mouth is completed with twelve permanent molars in each jaw, or twenty-four in all (Plate V.). The incisors are six in number in each jaw when the mouth is complete, at the age of four. Just back of these, on each side, at the age of four appears a pointed tooth called a tusk (Plate VI.). These tusks are rarely found in mares. The lower jaw of a horse three years old is marked by two permanent teeth in the centre and two milk teeth on either side. Milk teeth are easily distinguished from permanent incisors by their smallness, whiteness, and their more distinct necks. At the age of four the lower jaw has four permanent and one milk tooth on either side. At the age of five there are six permanent teeth and no milk teeth. At the age of six there are six permanent teeth and the corner teeth are filled in the centre. At the age of seven the dark filling in the pit of the two centre teeth disappears (Plate VI.). At the age of eight (Plate VI.) the dark filling disappears from the four centre teeth, and at the age of nine these marks have generally disappeared from all the teeth (Plate VI.). For all practical purposes this measure of the age of the horse is accurate enough, though it is apparent that the nature of the food on which the horse is fed, whether it be hard or soft, makes a difference. Horses, for example, fed upon the fresh food of a farm will retain the marks in the teeth longer than horses grazing upon tough grass. As a rule, in examining a horse's mouth only the lower jaw is looked at. It is well to lift the lips above the upper incisors to see if they are unduly worn—a sure sign of "cribbing."
PLATE XIII.—GOOD SHOULDERS, LEGS, AND FEET
PLATE XIV.—HEAVY-HARNESS TYPES