30 
DISPLACEMENT OF THE TEETH. 
viewed from in front, are inclined to the horizontal, their outer borders 
being T 3 g to f of an inch lower than their inner. If the lines of the grinding 
surfaces are prolonged, they meet in an obtuse angle below the palate. 
(Fig. 6.) Baume places the teeth of the horse in a class between those 
which grow continuously, and have an open pulp cavity, and those like 
the teeth of men and carnivora, the pulp cavity of which is closed, and 
which grow from the root. 
The ox’s molars differ from those of the horse in having a much 
rougher grinding surface. The edges of the folds of enamel project 
prominently, forming, even in normal teeth, quite sharp points. The 
lower rows of molars lie almost parallel with each other, or, at most, are 
Fig. 6.—Normal position of the molars in the horse. 
slightly bowed outwards. Sometimes the upper and lower rows of 
molars altogether fail to coincide or to cover. In many cases, when 
seen from in front, the outer edges of the lower molars are at the same 
height as the inner edges of the upper. The grinding surfaces are 
inclined as in the horse. Gunther states that the normal rate of wear, 
which in herbivora is very considerable, amounts to about 2 mm. 
(nearly one line) per year. In consequence of this continued wear, the 
grinding and cutting surfaces should eventually attain perfect contact. 
But where they do not, certain areas are insufficiently worn, and grow 
abnormally fast (Exsuperantia dentis, Kitt), while certain others wear 
too quickly. Hence arise the following irregularities :— 
{a) The angular or sharp mouth. 
(b) The shear-like mouth. 
(c) The wave-formed mouth, where the row of teeth, seen from the 
side, appears undulatory. 
(d) The step-formed mouth, where, from similar irregular wear, the 
row is composed of alternate high and low teeth. 
(e) Premature wear of the teeth. 
(/) The smooth mouth. 
