. The animal kingdom; based upon the writings of the eminent naturalists, Audubon, Wallace, Brehm, Wood and others. Mammals. CHAPTER I. RATS AND MICE. THE ORDER RODENTIA—THE FAMILY MURID/E—RATS AND MICE—THE BLACK RAT—THE BROWN- RAT—THE MOUSE—THE HARVEST MOUSE—THE BARBARY MOUSE—THE HAMSTER—THE MUSK RAT—THE WATER RAT—THE FIELD MOUSE—WILSON'S MEADOW MOUSE—LE CONTE'S MOUSE —THE COTTON RAT—THE LEMMING. THE RoDENTiA or Gnawers (from the hatin rodcre " to gnaw "), constitute a well-defined order characterized by the possession of two long, curved, sharp-edged, rootless incisors in each jaw.
. The animal kingdom; based upon the writings of the eminent naturalists, Audubon, Wallace, Brehm, Wood and others. Mammals. CHAPTER I. RATS AND MICE. THE ORDER RODENTIA—THE FAMILY MURID/E—RATS AND MICE—THE BLACK RAT—THE BROWN- RAT—THE MOUSE—THE HARVEST MOUSE—THE BARBARY MOUSE—THE HAMSTER—THE MUSK RAT—THE WATER RAT—THE FIELD MOUSE—WILSON'S MEADOW MOUSE—LE CONTE'S MOUSE —THE COTTON RAT—THE LEMMING. THE RoDENTiA or Gnawers (from the hatin rodcre " to gnaw "), constitute a well-defined order characterized by the possession of two long, curved, sharp-edged, rootless incisors in each jaw. The order contains a very considerable number of subdivisions, namely, sixteen families, some of which comprise over .two hundred species. It may be inferred from this fact that the animals of the order differ very widely in all other respects than that which has given them their name. The gnawing teeth are necessarily placed in strong heavy jaws which are large in proportion to the head, for they not only require a stout support, but room for continual development. These teeth are worn continually by the friction they undergo, and necessitate a provision for their continual renewal; the base passes deepl}^ into the jawbone, where a pulpy core supplies the material for constant growth. As those of the upper jaw meet those of the lower jaw at the tips, they are perpetually worn away by their action upon each other, and upon the hard food which they are formed for nibbling. The growth at the base and the wearing away of the tips thus balance each other. If one of the incisors is lost, the opposing one in the other jaw being no longer worn, grows till it projects like the tusk of an elephant. These incisors are chisel- shaped, and are provided in front with a layer of enamel hard as the hardest steel, while behind they are composed of a much softer material. Please note that these images are extracted from scanned page images that may have been digit
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectmammals, bookyear1897
