Thus, for example, the gnawing animals or _Rodents_, and the insect-eaters or _Insectivores_, are undoubtedly the lowest types next to the sloths and armadilloes, the insect-eaters especially having very primitive skeletons and small brains. Yet we shall find that we pass very naturally from them to the intelligent monkeys, while, on the other hand, the vegetable-feeders and flesh-eaters go off upon quite a different line of their own. Let us, then, begin with these two lowly groups, the _Rodents_ and _Insectivores_, and see how they have conquered their humble place in the world. One thing is clear, that they do not hold it by strength or audacity, for taken as a whole they are small and weak animals; the giants among rodents, the Capybaras of South America, where all lower kinds of animals thrive, are only as large as good-sized pigs, and the smallest, the “Pocket-mice” of North America, are not bigger than large locusts; while the insect-eaters have nothing larger than the “Tenrecs” or soft-bristled hedgehogs of Madagascar, about the size of a tailless cat; and the rest of the group vary from two to eight inches all over the world. Moreover, they are as a rule timid, and though some of them fight fiercely among themselves, yet they scamper away and hide at the least alarm, and generally choose the twilight or the dark night for their feeding time. Stroll out some fine summer’s evening, when the sun has set and the moon has not yet risen, and as you wander in the fields and woods with eye and ear open, you will scarcely have gone far before you will be aware that there is plenty of stir going on. Some active little field-mouse will cross your path in her eager search for grain and seeds to lay up for her winter store, or you may startle a hare in the long grass and watch her run across the field, or see her sit upright on her haunches surveying the quiet night-world. Or, if you pass over a common, the number of little white tips glancing in the twilight from under the furze bushes will tell you that the rabbits have not yet disappeared into their burrows; while as you enter the wood the sharp little eyes of the squirrel will peep down upon you from the beech trees, as she watches over her little ones in their comfortable nest in the branches. All these are _Rodents_, and you may know them by their four long chisel-like front teeth (see B, Fig. 55), which have a large gap on each side, between them and the grinding teeth behind. These chisel teeth have not bony roots like the teeth of most animals, but rest in a deep socket, and continue growing during the whole of the animal’s life; and they have a hard coat of enamel in front, so that as the tooth wears away behind, this enamel stands out and forms a sharp cutting edge, and there is perhaps no tool more efficient for gnawing a root, a nutshell, or the solid wood of a tree, than the tooth of a beaver or rat. [Illustration: Fig. 55.