IRREGULAR WEAR OF THE TEETH. 



275 



(B) IRREGULARITIES OF WEAR IN THE TEETH. 



In the horse's under jaw the rows of molars form two almost 

 straight lines, which posteriorly diverge slightly. In animals of 

 average size the first right and left molars lie about 2 inches, the 

 last about 4 inches, from each other. In the upper jaw the space 

 between the two rows (which are bowed outwards) is considerably 

 greater, the two first molars standing about 3 inches, the last molars 

 about 4 to 4| inches from each other. At the boundary between 

 the pre-molars and molars the cross measurement in the upper jaw 

 is about 4£ to 4| inches, in the under jaw about 3| inches. It will 

 thus be obvious that during rest the grinding surfaces of the upper 

 and lower rows do not cover each other ; the upper row overhangs 



Fig. 274. — Normal position of the molars in the horse. 



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. 274). Moreover, the grinding surfaces, when 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. 274). 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 are 

 prominent, forming, even in normal teeth, quite sharp points. The 

 lower rows of molars lie almost parallel with each other, or, at most, 

 are slightly bowed outwards. Sometimes the upper and lower rows 

 of molars altogether fail to coincide or to cover. In many cases, 



T 2 



