INJURIES IN THE INTERDENTAL SPACE. 
23 
teeth and the alveolar margin of the hone appear movable, or are more 
or less displaced backwards. The upper lip often hangs down obliquely, 
so that on casual examination this injury might be mistaken for facial 
paralysis. So long as the fracture is confined to a single alveolus or 
to the nasal process, it heals rapidly and completely. Transverse 
fractures of the body give greater trouble, especially when the alveolar 
margin and the incisors are movable, or when a complicated fracture 
exists. Treatment of such cases is only advisable in valuable or 
favourite animals. Where the free edge is firm, recovery is much more 
certain. 
Treatment aims at fixing the fragments in position with wire 
in the same way as in the lower jaw. In complicated fractures 
strict antiseptic precautions must be observed. In some cases the 
incisor 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 inter-maxillary 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. Pteduction can often be effected, even 
several days after the accident, by using as a lever the thin 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 
strong, 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 seveie 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 aie heavy. 
The diseased processes so produced are of various kinds, and may be 
distinguished as follows :— 
(1) The simplest injury consists in erosion of the mucous membrane 
covering the interdental space. The epithelium being removed by the 
rubbing of the bit occasionally makes sensitive riding-horses trouble¬ 
some, but yields to treatment in a few days. 
