“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