268 I Nil III KS OF THE INTERDENTAL SPACE. 



teeth, which have been dislocated backwards, can only be replaced 

 in their normal position after the lapse of some time, and by 

 exercising considerable force. But as soon as they are brought into 

 position, so that the upper and lower teeth are in contact, the move- 

 ments of mastication usually suffice to complete replacement. In 

 horses transverse fractures of the premaxillary bone just behind 

 the alveolar process have often been seen : in one case the upper 

 incisors had all been thrust downwards and backwards in consequence 

 of the animal falling on the mouth. Reduction can often be effected, 

 even several days after the accident, by applying a steel hernia- 

 clamp, or by using as a lever the handle of a hammer. Sometimes 

 strong pressure with the thumbs is sufficient. 



(4.) INJURIES OF THE INTERDENTAL SPACE. 



The interdental space is that portion of the jaw which intervenes 

 between the corner incisor and the first molar tooth. The bone 

 here presents a more or less sharp border, and is covered with 

 periosteum and thick mucous membrane. On this part the pressure 

 of the bit falls. The bit usually rests on the tongue and edges of 

 the lips, but the action of the reins presses it against the jaw, and 

 thus, especially in riding-horses, produces wounds. The more severe 

 the bit, and the lower it is fixed, the more easily this happens. Such 

 injuries are also more frequent with a high and sharp conformation 

 of the bone, a thin tongue and relaxed lips, and with riders whose 

 hands are heavy. 



Unfortunately, wounds are often discovered only when the jaws 

 are considerably swollen. Injuries to the interdental space are very 

 common in the army after general manoeuvres, and when cavalry 

 ride great distances without veterinary superintendence. Under 

 such circumstances the mouths require to be examined as regularly 

 as the backs and saddles. In tender-mouthed horses leather or 

 rubber covered bits prevent this injury and should be used for some 

 time after healing ; but as long as wounds exist they are of little 

 service. 



The simplest injury consists in abrasion of the mucous membrane 

 covering the interdental space. The epithelium being removed by 

 the rubbing of the bit makes the mouth sensitive and the horse 

 troublesome for a few days. 



Should the force be greater, the mucous membrane will be bruised 

 or wounded. Infection and suppurative periostitis occur, the border 



