SPECIAL DEFECTS OF THE MOLAR TEETH 329 



In quite young horses the tables of the molars are practically level, 

 but in course of time they gradually take the direction of inclined 

 planes. The reason why the edges are not kept down by wear is said 

 to be that the upper jaw is wider than the lower one. It has been 

 observed that individuals acquire a habit of grinding their food with a 

 movement almost exclusively from right to left, and irregular wear of 



124.— Tooth-Rasp 



the teeth naturally follows as a consequence. When, from the presence 

 of a decayed or malformed tooth, the motion of the jaw is limited and 

 altered from its normal direction, irregularity is often observed to result 

 at the edges. 



The lower molars invariably wear away faster than the upper, but 

 it will be remembered that they are smaller to begin with; those in the 

 middle of the jaw are sometimes worn quite low, while those at either end 

 appear to have escaped a fair amount of work and remain prominent, the 

 surface altogether presenting an undulating character. 



Fig. 125.— Tooth-Shears 



We cannot alter the animal's manner of eating, but we can reduce 

 the sharp edges of his teeth from time to time, and remove parts that 

 project unduly. The former operation is accomplished with an instrument 

 known as a tooth-rasp (fig. 124), and requires a considerable expenditure of 

 energy on the part of the operator to perform it effectually. The latter 

 may require the use of tooth-shears. Rasping may often be done without 

 a gag, by simply drawing out the tongue on the opposite side to that 

 upon which the rasp is to be applied. Many horses submit to the pro- 

 ceeding with less opposition, when secured in this simple manner, than 

 they would do if twitch and gag were called into requisition. When 

 the tooth-shears (fig. 125) are to be used, the animal will require to be 

 under more thorough restraint, and is most favourably placed for the 

 operation when cast. 



