IRREGULAR DEVELOPMENT OE THE TEETH. 273 



may have undergone atrophy. The eruption of the molars seldom 

 gives rise to trouble, though at times severe pain accompanies the 

 process, and soft food may be required. Occasionally, however, the 

 animal loses condition to such a degree as to necessitate operative 

 interference. Frick removed six temporary molars from a foal's 

 mouth ; they had remained fixed on the erupting teeth like caps, 

 and during mastication continually injured the gums and cheeks. 

 The animal's appetite and condition immediately improved after 

 the operation. 



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 

 another of the permanent 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 displaced. 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. In overshot jaw the case is reversed. The teeth consequently 



