Hair, wool, fur, and animal down are simply slender filaments or thread-like fibres issuing out of the pores of the skins of animals, and all partaking of the same general nature, such as great ductility, flexibility, elasticity, and tenacity, differing entirely from the vegetable wools and downs, such as cotton, &c., which contain neither of these four great characteristics to any valuable or appreciable extent. To characterize in a familiar way these several grades of material, it may be said that fur is distinguished from wool by its greater fineness and softness, and hair from wool by its straightness and stiffness. The nature of all these bearing some relation to each other, it will be necessary in this treatise to use the word hair occasionally to designate one and all of them, that word being most convenient, and tending to avoid confusion. Simple as the idea may be, and though trifling in appearance, yet the study of a single hair is particularly interesting, both to the naturalist and the man of business, as will be seen when we mention a few of its many peculiarities; hoping it will prove a source of enjoyment to the one and a profit to the other. Hair, wool, fur, &c., form quite an extraneous appendage to the skin, or body producing them, not at all directly dependent on the life of the animal for their own existence, for they have been known to live and grow for some time after the death of the animal itself. We also know that they live, grow, and die, showing all the signs of youth, maturity, and old age. Hair possesses no sensation at any period of its existence; of itself it has no feeling of touch, nor has it the power of voluntary action. The growth of hair is peculiar as it projects and grows in length from the root, and not by the top as with vegetable productions, the lower portion lengthens out, and the top is merely projected forward; and when once cut, it never again resumes its tapering point. Hair or fur of whatever quality, consists of a single slender filament, without a branch or knot of any kind, and that filament is a tube, which is filled with a fat oil, the color of the hair being derived from this oil.