THE TEETH. 

 Fig. 7. 



179 



The full-grown dog has usually 20 teeth in the upper, and 22 in the 

 lower jaw, with two small supernumerary molars. All of them, with the 

 exception of the tushes, are provided with a bony neck covered by the 

 gums, and separating the body of the tooth from the root. The projecting 

 portion of the teeth is more or less pointed, and disposed so as to tear 

 and crush the food on which the dog lives. They are of a moderate size 

 when compared with those of other animals, and are subject to little loss 

 of substance compared with the teeth of the horse. In most of them, 

 however, there is some alteration of form and substance, both in the inci- 

 sors and the tushes ; but this depends so much on the kind of food on 

 which the animal lives, and the consequent use of the teeth, that the indi- 

 cation of the age, by the altered appearance of the mouth, is not to be 

 depended upon after the animal is four or five years old. The incisor 

 teeth are six in number in each jaw, and are placed opposite to each other. 

 In the lower jaw, the pincers, or central teeth, are the largest and the 

 strongest ; the middle teeth are somewhat less ; and the corner teeth the 

 smallest and the weakest. In the upper jaw, however, the corner teeth 

 are much larger than the middle ones ; they are farther apart from their 

 neighbours, and they terminate in a conical point curved somewhat in- 

 wards and backwards. 



As long as the teeth of the full-grown dog are whole, and not injured 

 by use, they have a healthy appearance, and their colour is beautifully 

 white. The surface of the incisors presents, as in the ruminants, an in- 

 terior and cutting edge, and a hollow or depression within. This edge or 

 border is divided into three lobes, the largest and most projecting forming 

 the summit or point of the tooth. The two lateral lobes have the appear- 

 ance of notches cut on either side of the principal lobe ; and the union of 

 the three resembles the fleur de Us, which, however, is in the process of 

 time effaced by the wearing out of the teeth, (figs. 3 & 4.) 



While the incisor teeth are young, they are flattened on their sides, and 

 bent somewhat backwards, and there is a decided cavity, in which a pulpy 

 substance is enclosed. This, however, is gradually contracted as the age 

 of the dog increases. 



M. F. Cuvier speaks of certain supernumerary teeth occasionally de- 



N 2 



