28 
IRREGULAR DEVELOPMENT OF THE TEETH. 
mastication continually injured the gums and cheeks. The animal s 
appetite and condition immediately improved after the operation. 
(c) DISPLACEMENT OF THE TEETH. 
Molars may become displaced in consequence of disease of the alveolar 
periosteum and loosening of the teeth. This condition will be noticed 
later. Abnormalities occur in development; one or other of the per¬ 
manent incisors, instead of appearing in the site of the deciduous tooth, 
sometimes makes its appearance at a point further back, and wounds the 
tongue. Stockfleth mentions a case of this kind. 
In horses an incisor is sometimes rotated on its axis, the convex surface 
being turned inwards, or it lies horizontally, and grows beyond the lips, 
injuring the animal’s appearance. The molars may be similarly dis¬ 
placed. Kitt describes a mouth in which the first molar lay with its 
crown alongside the outer aspect of the second and fourth, whilst its root 
projected from the jaw on the inner side at a point about an inch and a 
half below the alveolar ridge. 
Kitt ascribes such deviations from normal position either to temporary 
or permanent want of space at the time the tooth appears, or to abnormal 
conformation of the mouth or incidence of pressure. A milk tooth may 
thus give an abnormal direction to a permanent tooth just developing, 
or this abnormal direction may exist from the first. 
False position, due to irregular development of the jaw, may be 
considered under this heading. Either jaw may be affected. If the 
upper is too long (Prognathia superior), or the lower too short 
(Brachygnathia inferior), the so-called “overshot jaw” is the result; 
whilst an opposite conformation produces “ undershot jaw.” These 
variations result from faulty development of the bones, and are often 
accompanied by corresponding changes in the molars. In undershot 
jaw the lower rows of molars are displaced anteriorly so that the first 
lower molar projects beyond that of the upper jaw, whilst the last 
upper molar does not come in contact with its fellow of the lower jaw 7 . 
In overshot jaw the case is reversed. The teeth consequently either 
partially or entirely escape wear, and thus become too long and 
impede mastication. The nose, or even the entire head, may be distorted, 
producing displacement of the teeth. This is termed by Gurlt campylor- 
hinus. (Fig. 11.) Leisering saw such a case during life. Dose noted 
a peculiar abnormality in a cow. The incisors stood in pairs, one 
behind the other. Although the animal was three years old, no teeth 
had been shed. The under jaw was deformed, and Gurlt considered 
this to be the real and primary cause of the peculiarity. 
When slight, these changes are of little importance, but immediately 
they become pronounced they produce various undesirable results. The 
