Page:Natural History (1848).djvu/220

210 becomes in cold countries grey in winter, and even in England this change takes place, though in a slight degree. The long pencilled hairs with a which the ears are furnished are lost during summer.

The very extensive group of small rodent animals which have received the name of Rats and Mice, have in each jaw, besides the two incisors common to the Order, three molars on each side, fixed by distinct roots, the crowns of which are surmounted by blunt tubercles, which when worn down assume the form of a disk variously indented. The teeth of the upper jaw shelve backwards, those of the lower forwards. The tail is long, round, and tapering to a point&#59; furnished with short hairs or scattered bristles, growing at intervals from beneath scaly rings formed by the outer layer of the skin (epidermis). ‘There are wae &#59; five toes on the hind feet, and usually four on the anterior, with the slight rudiment of a thumb: the feet are neither webbed nor fringed with stiff hair&#59; though several species swim with facility. The fur is often intermixed with longer bristles, or flat spines.

The ordinary food of the animals before us consists of grain, seeds, and farinaceous vegetable substances&#59; and for the bruising of these the structure of their teeth is adapted. Yet we might infer from it that animal food would not be rejected by them: and experience abundantly proves this to be the case. The depredations of our most