Page:Natural History (1848).djvu/148

138 as the growth of the jaw is stopped, the succession of the teeth is arrested also, which fixes the duration of the animal’s life."

The structure of the teeth will be understood by the following extract from a paper which was subjected to Mr. Corse’s revision, in Brewster’s Edinburgh Encyclopædia:—

"The Elephant has no cutting-teeth in either jaw in front; but he is furnished with most powerful grinders, that enable him to bruise the vegetables on which he feeds. These teeth, as in all herbivorous animals, have an uneven surface; but do not rise into points, as in animals which feed on flesh. Each grinder is composed of a number of perpendicular lamine, which may be considered as so many teeth, each covered with a strong enamel, and joined to one another by a bony substance of the same quality as ivory. This last substance, being: much softer than the enamel, wears away faster. by the mastication of the food, so that the enamel: remains considerably higher; and in this manner, the surface of each grinder acquires a ribbed appearance, as if originally formed with ridges. From very accurate observations which have been made on the Asiatic Elephant, it appears that the first set of grinders, or milk-teeth, begin to cut the jaw eight or ten days after birth, and the grinders of the upper jaw appear before those of the lower one. These milk- grinders are not shed, but are gradually worn away during the time the second set are coming forward, and as soon as the body of the grinder is nearly worn away, the fangs begin to be absorbed. From the end of the second to the beginning of the. sixth