A Natural History of the Mammalia, Vol. 2

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Excerpt from A Natural History of the Mammalia, Vol. 2: Containing the Order Rodentia, or Gnawing Mammalia, With 22 Illustrations Engraved on Steel, and Engraving on WoodSquirrel and Rat families. Sometimes the width of the incisor is very great, and exceeds the depth, the Rodents, which burrow, and live almost entirely under ground, present this form of incisors, these powerful teeth being no doubt used to gnaw through the roots, which would otherwise obstruct their subterranean course. Other modifications in the form of the incisor teeth will be hereafter pointed out in the de scriptions of the various species, I shall merely here oh serve, that those of the upper jaw are always shorter than those of the lower, and usually describe about three parts of a circle. The longer incisors of the lower jaw form a smaller segment of a larger circle.Owing to the unequal density of different parts of the incisor teeth, the wear by their mutual attrition is unequal, the softer hinder part wears most rapidly, and the hard enamel in front least so hence a sloping, chisel-like edge is always preserved. In proportion as the exposed end of the incisor is thus worn, additional dentary matter being supplied to the tooth, it continues to grow from the base, and thus preserves an uniform size.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.