284 DISEASES OF THE TOOTH PROPER. 



THE SMOOTH MOUTH. 



Enamel and dentine being of unequal hardness, the latter wears 

 away more rapidly and produces the roughened fold-like appearance 

 on the grinding surface of the molar, requisite for effectively 

 triturating the food. But when enamel and dentine wear at the 

 same rate the surface becomes even and polished. In advanced age 

 this normally occurs, because in the deeper portions of the tooth 

 the enamel ceases. It also occasionally occurs in young animals 

 on account of insufficient hardness and durability of the enamel, 

 and is more serious than in older horses. The smooth mouth during 

 mastication resembles an uncut millstone during grinding. Masti- 

 cation is of course less impeded when single teeth are affected than 

 when the condition is general. 



Treatment is confined to palliatives, giving crushed or ground 

 grain, gruel, or bran mashes, and allowing longer time for feeding 



The opposite condition in horses is termed " ruminant's mouth." 

 The grinding faces become exceedingly uneven. This is normal, 

 however, so long as the molars have not come into wear ; but it 

 rarely persists, and is seldom troublesome. 



(C) DISEASES OF THE TOOTH PROPER. 



DENTAL CARIES (CARIES DENTIUM). 



The term " Caries " is used to describe the process which results 

 in the decay or destruction of the cement, dentine and enamel of the 

 teeth, the enamel, by its structure and resistance, being more slowly 

 destroyed than the other constituents of the tooth. At one time 

 Moller was doubtful whether caries occurred in animals, but Kitt's 

 observations and his own later experience show that this opinion 

 was not strictly correct, and he has lately reported some cases of 

 undoubted caries in the molars of horses. Kitt has pointed out 

 that in animals it takes the form of dry chronic caries, and Baume 

 has noted the same fact in connection with ruminants and dogs. 

 He states that the process starts either in the cement of the enamel 

 folds, or in the centre of an " island " of dentine. Stockfleth and 

 Kitt believe that caries starts in the remains of the osteo-cement 

 pulp, that is, in the tissue which in the embryo forms the cement. 

 This material, or at least the space left by its contraction, is seen 

 when a tooth is cut through with the shears. It begins just below 

 the grinding surface, and reaches downwards as far as the involution 

 of the enamel. Sometimes it is even visible on the grinding surface, 



