CHAPTER III

The Teeth As An Indication of Age

When a colt is born the first and second temporary molars, three on each jaw, are to be seen. These are large when compared with the size of those that later replace them. In from five to ten days after birth the two central incisors or nippers make their appearance. In three or four weeks the third temporary molars appear, followed within a couple of months by an additional incisor on each side of the first two, both above and below. The corner incisors appear between the ninth and twelfth months after birth. This makes the full set of teeth--twenty-four in number.

There is now no change in number, although there is considerable change taking place all the time; the incisor teeth, in rubbing against each other, are more or less worn, giving rise to the expression “losing the mark.”

The two molars present at birth remain until the animal is about three years old, at which time they fall out of their sockets by the protrusion of the second set, or permanent molars.

This change from temporary to permanent teeth takes place usually without difficulty and without trouble. The permanent teeth push their way up from below crowding those in view. While this pushing and crowding is going on the temporary teeth are losing ground, for the reason their roots are being absorbed, and a time comes when the cap only is left attached to the gums. This cap drops out and the new or permanent tooth soon is established in its place.

LOSING OF TEMPORARY TEETH

According to the observation of Mayo, the temporary incisors are replaced by permanent teeth as follows: “The two central incisors are shed at about two and a half years, and the permanent ones are up ‘in wear’ at three years. The lateral incisors are shed at three and a half and the permanent ones are up and in wear at four years. The corner incisors are shed at four and a half and the permanent ones are up and in wear at five.

“The molars are erupted and replaced as follows: The fourth molar on each jaw (which is always a permanent molar) is erupted at ten to twelve months; the fifth permanent molar at two to two and a half years, and the sixth usually at four and a half to five. The first and second molars, which are temporary, are shed and replaced by permanent ones at two to three years of age. The third temporary molar is replaced by a permanent one at three and a half years. In males, the canine or bridle teeth are erupted at about four and a half years of age. At about five years of age a horse is said to have a full mouth of permanent teeth.”

THE MARK IN THE TOOTH

Horsemen make use of the “mark in the tooth” for determining the age between five and eleven. In examining teeth you observe that two bands of enamel are to be seen; one exterior, that surrounds the tooth, the other interior, which is termed the casing enamel. It is this latter, or “date cavity,” that is used to tell the age.

The mark in the tooth is occasioned by the food blackening the hollow pit. This is formed on the surface by the bending in of the enamel, which passes over the surface of the teeth, and, by the gradual wearing down of the enamel from friction, and the consequent disappearance of it, the age can be determined for a period of several years.

When a horse has attained his sixth year the mark on the central or middle incisors or nippers of the lower jaw will be completely worn off, leaving, however, a little difference of color in the center of the teeth. The cement which fills the hole produced by the dipping in of the enamel will be somewhat browner than that of the other portions of the tooth, and will exhibit evident proofs of the edge being surrounded by enamel.

At seven years the marks in the four middle incisors are worn out and are speedily disappearing in the corner ones. These disappear entirely at the age of eight; thus all marks are obliterated at this age on the lower jaw; the surface of the teeth are level and the form of the teeth changes to a more oval form.

The marks on the upper jaw are still present, since there has been less friction and wear on them. At nine the marks disappear from the central upper incisors, at ten from the adjoining two, and at eleven from the corner teeth.

To tell the age of the horse beyond this period is difficult and uncertain, except by those very much experienced in performing the undertaking. The shape of the teeth, the color and the condition all enter into the determination but there is no fast and fixed rules after the marks have disappeared.

TEETH OF CATTLE

Cattle have no incisor teeth on the upper jaw. They have eight incisors on the lower jaw. According to Mayo, the temporary incisors are as follows: “The central incisors or nippers are up at birth, the internal lateral at one week old, the external lateral at two weeks, and the corner incisors at three weeks old. They are replaced by permanent incisors approximately as follows, though they vary much more than in the colt: The central incisors are replaced at 12 to 18 months; the internal laterals at about two and a half years; the external laterals at three to three and a half years; and the corner incisors at about three and a half years. In the horned cattle, a ring makes its appearance at three years of age, and a new ring is added annually thereafter.”

TEETH OF SHEEP

Sheep, like cattle, have no incisor teeth on the upper jaw. Like cattle, they have eight incisors on the lower jaw when the mouth has reached full age. The change of the teeth occurs as follows: At birth the lamb has two incisors, followed by two more very soon. At the end of two weeks two more are out, making six incisors in all. At three weeks of age two more have appeared, completing the appearance of the temporary or milk teeth.

The permanent begin to replace the temporary teeth between one and one and a half years. The two central milk teeth are first replaced by two longer and stronger teeth. The lamb is now known as a yearling.

At two years the two teeth adjoining the central incisors are replaced by permanent ones; at three the two adjoining these are replaced, making now six permanent incisors.

Between four and four and a half the last two permanent incisors appear and the sheep then has a full mouth.