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.
[Illustration: LUMPY JAW
The disease is caused by the ray fungus. The result is local tumors in
the bones and other tissues.]
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.