The body of the beaver contains a curious odoriferous substance, called by the trappers barkstone, but more scientifically "castor," or "castoreum." It is contained in two little bags about the size of a hen's egg, and is of a brownish, unctuous consistency. At one time it was supposed to possess valuable medicinal properties. It is now, however, chiefly employed by perfumers. The beavers themselves are strangely attracted by this substance, and when scenting it at a distance will invariably make their way to it. It is said that the inhabitants of a particular lodge go forth, and having rid themselves of their superabundant castoreum at a little distance, return home; when the beavers of another lodge, scenting the castoreum, proceed to the same spot, and covering it over with a layer of earth and leaves, deposit their own castoreum upon the heap. After a time, the former beavers go through the same process; and this is continued until a mound of three or four feet in height has been raised. It is difficult to account for the object of this strange proceeding. It was not, however, till of late years that the sagacious Indians discovered that the castoreum was a certain bait for the animals themselves. Formerly, the bait they employed was a piece of green aspen, beaten up, and placed near the trap. At length an Indian tried whether a male might not be caught by adding some of the castoreum. By that time steel traps had been introduced, instead of the clumsy wooden traps before used. Not only were the males caught, but the females also; and the trappers were now able with their steel traps to catch vast numbers of the infatuated animals. It is said that the creatures, when perceiving the scent, will sit upright, snuffing about in every direction, and squealing with excitement. The younger animals, however, are those chiefly caught. The old ones are often too cunning; and it is affirmed that, instead of touching the bait, they will cover up the trap with mud and stones till a mound has been raised, and then, depositing their superabundant castoreum upon it, take their departure.