The walrus is not quite so large as the sea-elephant, nevertheless, it is a very big animal, for a full-grown male will often measure twelve feet in length, and will weigh nearly a ton. It uses its tusks for many different purposes. When it wants to climb upon an ice-floe, for example, it will dig them deeply into the ice, and so obtain purchase while it raises its huge body out of the water. They are very formidable weapons, too, and the animal can strike so quickly with them, both sideways and downward, that it is not at all easy to avoid their stroke. Then they are very useful in obtaining food. If a walrus finds the body of a dead whale, it will cut off huge lumps of the flesh by means of its tusks; and very often it will dig in the sandy mud with them for mussels and cockles. The consequence is that the tusks are frequently broken, while they are nearly always very much worn at the tips. The name walrus is a corruption of whale-horse. The animal is sometimes known as the sea-horse, and also as the morse. CHAPTER XIII THE WHALE TRIBE The whales are more thoroughly creatures of the water than even the seals, for they never come upon dry land at all, even during the breeding-season. Indeed, if a whale is unfortunate enough to be thrown upon the shore by a great wave, and left stranded, it cannot possibly make its way back into the sea, but is obliged to lie there till it dies. Yet we must not think that these giant creatures are fishes; for they are as truly mammals as the seals are. Their blood is hot, and is driven through the body by a heart made up of four chambers, instead of only two. They breathe by means of nostrils and lungs, and not by means of gills. And besides that they suckle their young, just as all other mammals do. Then, once more, if you look at the body of a whale, you will see that its tail is quite different from that of a fish. The tail of a fish is upright, but that of a whale is set crosswise. So that there is only one respect in which whales are really like fishes, and that is the general shape of the body. These huge animals fall naturally into two families, the first consisting of those which have teeth, and the other of those which have whalebone, or baleen, instead. But in many ways the members of both these families are alike. HOW WHALES BREATHE