IRREGULAR WEAR OF THE TEETH. 
29 
animal has difficulty in grazing, can no longer tear off the short grass, 
and where the incisors are much affected mastication even of cut food 
may prove difficult and painful. If the molars fail to correspond, the 
grinding surfaces wear away unevenly, and the overlapping part grows 
until it either wounds the opposite gum or even the palate, and thus 
produces pain in chewing. Deviation of the axis of the tooth in eithei 
a backward or forward direction, is continually aggravated by masti¬ 
cation, which tends still further to thrust the tooth out of position and is 
apt finally to produce alveolar periostitis. 
Schrader saw a horse in which the first left upper molai was 
immediately behind the tush, while the second lay at the innei side of 
the third, so that the first molar was separated from the otheis by a 
space of 2 inches. The two first lower molars had giown into this 
space and perforated the palate, and in drinking, the water passed 
through this aperture and was discharged by the nostiils. The hoise, 
being much wasted,' was slaughtered. 
Too great a space between the teeth is at once abnoimal and injurious, 
especially in the case of the molars. The crowns of the teeth should 
stand close together, so as to afford mutual support, and. prevent 
food entering the interspaces. Where intervals occur food is driven 
into them, penetrates even the alveoli, and may produce inflammation 
there. Such alveolar periostitis is not uncommon in old animals. 
Treatment consists in shortening or removing the offending tooth. 
In young animals too much of the tooth must not be removed at once, 
as the pulp cavity may be exposed, and alveolar periostitis set up. 
Where intervals occur between the teeth the evil is palliated by giving 
soft food, so as to lessen or remove the need for mastication. 
(B) IRREGULARITIES OE WEAR IN THE TEETH. 
In the horse’s under jaw the rows of molars form two almost stiaight 
lines, which posteriorly diverge slightly. In animals of average size the 
first pair of teeth lie about 2 inches, the last about 4 inches, fiom each 
other. In the upper jaw the space between the two rows (which are bowed 
outwards) is considerably greater, the two first molars on either side 
standing about 3 inches, the last molars about 4 to 4J inches from each 
other. At the boundary between the pre-molars and molars the cioss 
measurement in the upper jaw is about 4J to 4f inches, in the under 
jaw about 3i inches. It will thus be obvious that during rest the 
grinding surfaces of the upper and lower rows do not cover one another ; 
the upper row overhangs the outer edge of the lower ; while, on the 
other hand, the inner edge of the lower row projects farther inwards 
than that of the upper. (Fig. 6.) Moreover, the grinding surfaces, when 
