A set of teeth consists of three different kinds. Those situated in front or anterior part of the mouth are called the _incisors_, and those placed immediately behind the incisors are called the _tusks_ or _canines_, and behind those are the _molars_. Each tooth is divided into three parts. The free, or part that is seen when looking into the mouth, is called the crown; then there is the neck or constricted part, which is encircled by the gum, and divides the crown from the fang or root, which is inserted in a cavity (the Alveolus) in the jaw-bone. Each tooth is made up of three different structures. The external, or enamel, which gives the new tooth its beautiful white appearance, and consists only of a somewhat thin layer, and covers the crown of the tooth only. Immediately underneath the enamel, is situated the ivory or dentine, of which the tooth, including the fang, principally consists. In the centre of the fang is a foramen, or small cavity, containing the pulp, consisting of a membrane nerve and small blood-vessels to supply nourishment, etc., to the tooth. The _incisors_, twelve in number, both in the temporary as well as in the permanent set, are for distinction divided into _nippers_, which are the two centre ones; the _intermediates_ are those situated between the nippers and _corners_, the latter being placed next to the tusks. The crown of an incisor tooth presents three prominences—a middle, which is the strongest, and two lateral. On the internal surface of the tooth is noticed a slope, somewhat resembling that found in an ox’s or sheep’s tooth. The root is well developed, longer than the crown, and flattened on both sides. The tusks, four in number, in both sets are strong, elongated organs, conical in form, and curved in an outward and backward direction. The upper fangs are the strongest, and there is a small space between them and the corner incisor teeth, in which the lower tusks are situated when the mouth is closed. Most of the molars terminate in sharp lobes, and, consequently, are well adapted for tearing and crushing. They are, as a rule, twenty-six in number, seven on each side of the lower jaw, and six on each side of the upper one; but sometimes there are seven on each side of the upper jaw, the same as the lower. It is not an uncommon occurrence for a dog with a short face, like bulldogs, spaniels, and pugs, to have only five upper molars, and six lower molars. But there are only twelve temporary molars—three on each side of both jaws. A puppy, when born, has no teeth visible, though the milk ones are formed and in the gums, and in some cases, their outline may be seen through the mucous membrane. The milk teeth are smaller, softer, and more pointed than the permanent ones, and they are not situated so closely together. The tusks, too, are slightly pink in colour just above the neck, which is not the case with the second ones.