DISEASE'S OF THE MOUTH AND TONGUE. 47 



The full-grown dog has usually twenty teeth in the upper 

 and. twenty-two in the lower jaw, with two small supernume- 

 rary molars. All of them, with the exception of the tushes, 

 are provided with a long neck covered by the gums, and sep- 

 arating 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 moderate size when compared with those of other ani- 

 mals, 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 incisors 

 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 indication 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, arid 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 further apart from their neighbors, and they 

 terminate in a conical point, curved somewhat inwards 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 

 color is beautifully white. The surface of the incisors pre- 

 sents, as in the ruminants, an interior 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 

 appearance of notches cut on either side of the principal lobe, 

 and the union of the three resembles the j^eur de lis, which, 

 however, is in the process of time effaced by the wearing out 

 Df the teeth. (Figs. 6 and 7.) 

 While the incisors are young they are flattened on tiieir 



