Besides, the sperm whale has a hump on his back, which distinguishes him from others. This hump is farther forward than the fin on the finback whale. Sperm whales have been captured from seventy to ninety feet in length, and from thirty to forty-five feet in circumference round the largest part of their bodies. It is supposed by whalemen, from their appearance, that they live, or some of them at least, to a great age. One writer on this subject thought that the sperm whale would attain the age of many hundred years, and even to a thousand years. This, however, is mere conjecture, because there are no dates or facts upon which to found a correct opinion. Some whales have been taken having their teeth worn off level with the gums; and then, again, in other instances, part of their teeth have been broken off, or torn out by some violent effort. The whole number of teeth in a sperm whale is about forty-two; they are wholly in the lower jaw, which alone is movable, with the exception of a natural movement of the entire head of the fish. The teeth admirably fit into sockets in the upper jaw. When the whale is in search for his food, or contending with his foes, he drops his lower jaw, if he sees fit, nearly to a right angle with the under part of his body, and then brings his jaws together with incredible energy and quickness. Sperm whales engage in fearful and dreadful struggles and conflicts with each other. One was captured, a few years since, having his lower jaw, which was more than fifteen feet long, and studded with sharp-pointed teeth, twisted entirely around at a right angle with his body; he was swimming in that manner when he was harpooned. This was an instance of a most desperate encounter. Another whale was captured having a part of his enormous jaw broken entirely off. The front and sides of their heads, as well as their bodies, not unfrequently exhibit deep lines or furrows produced by the teeth of some powerful antagonist. It is supposed that, as the sperm whale advances in age, his head not only retains its ordinary proportions, and to appearance becomes enlarged, but the truth is, the other parts of his body, especially his extremities, do actually diminish in bulk and circumference. In some instances, more oil has been taken out of the head of a sperm whale than from the other part of his body.