THE HORSE'S DII^I^ER TABLES. 61 



same as that of the upper teeth, but their transverse 

 diameter is nearly a half less. 



The broad crowns of the upper teeth form what are 

 called by veterinarians " tables," whereon the food is 

 ground or kneaded by the narrow-crowned opposite 

 grinders, the lateral movement of the lower jaw ena- 

 bling the latter teeth to pa^ over the entire extent of 

 the former. 



The crown surfaces of the upper and lower rows are 

 slanting instead of level, the former slanting inward, 

 the latter outward. The inclined-planes are thus in 

 perfect opposition, and yet in perfect harmony, for they 

 facilitate the lateral and semicircular movement of the 

 lower jaw during mastication. 



The figures formed by the upper and lower rows of 

 grinders, aside from the difference in their thickness, 

 are very dissimilar. The upper rows are slightly con- 

 cave, and converge in conformity to the narrowing of 

 the jaws; the space between the sixth grinders averages 

 about two inches and four-fifths, while that between 

 the first is about two inches. The lower rows form 

 regular but oblique lines, which also converge, like the 

 sides of a hopper, in conformity to the narrowing of 

 the jaws, the space between the two sixth grinders and 

 the two first averaging respectively two inches and a 

 half and one inch and a half. Thus, when the mouth 

 is closed, the low^er teeth in the region of the sixth 

 grinders scarcely cover a third of the crown surface of 

 the upper teeth, while those in the region of the first 

 barely lap their inner edges. This apparent structural 

 defect is overcome by the lateral movement of the 

 lower jaw, which, owing to the fact that it increases 

 in proportion to the distance from its hinge-like joint 

 in the region of the temporal bone and zygomatic 



