TEETH OF THE LOWER ANIMALS. 41 



food being raw flesh, in its wild state, it rather required 

 to be cut or torn in pieces than ground, and the upward 

 and downward motion of the jaws is sufficient for this 

 purpose. 



Dr. B. This is the case, not only with the cat, but 

 with all carnivorous or flesh eating animals ; their mo- 

 lares also uniformly terminate in sharp points, and their 

 incisors are long and pointed. In herbivorous or veg- 

 etable eating animals, on the contrary, the molar teeth 

 are much larger and their faces present a rough and ir- 

 regular surface, the better to fit them for grinding hard 

 grains and tough herbage. 



Emily. Horses, oxen and some other animals ought 

 to have, I should think, teeth with the power and hard- 

 ness of mill-stones, to break down such hard, tough 

 substances as corn, hay and many other articles which 

 they feed upon. 



Dr. B. Their teeth are admirably calculated for 

 this purpose. They are very large, and are not only 

 surrounded by enamel, but vertical plates of this sub- 

 stance are found in the interior of the tooth, interposed 

 with its earthy parts, and rising to the surface of the 

 tooth. This prevents the tooth from wearing away as it 

 inevitably would, if the enamel were not present. 



Emily. I recollect now having observed, when I 

 have been looking at the teeth of a horse or ox, several 

 undulating, zig-zag lines on their surface. This is 

 caused I suppose, by the earthy substance being worn 

 away, and leaving the harder plates of enamel projecting 

 above them. But is this the manner in which the teeth 

 are always prevented from wearing away when subject 

 to considerable use ? 



Dr. B. It is in a great many animals, but in the 

 gnawing animals, such as the beaver, rat, squirrel, &c. 

 there is a very different contrivance. To be enabled to 

 cut through such hard solid bodies as they do with per- 

 fect ease, they are furnished with two " strong incisive 

 teeth in the front of each jaw. The enamel is found 

 4* 



