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Living bone is bluish pink, insensitive, and elastic; on exposure to air it becomes diseased and blackened, very sensitive and painful; (the teeth excepted) which are harder and of a higher specific gravity than any other bone formation.

Bones are composed of two kinds of substance—animal, which makes the bone tough and flexible; earthy, which makes it hard and fragile. In young animals the animal matter forms about one-half of the bone substance; in the adult, it diminishes to about a third, while in old animals it is still less; hence the bones of very old animals are brittle, more liable to fracture and harder to mend.

Bones in a six-year-old horse contained, Phosphate of Lime, 54.37 per cent; Carbonate of Lime, 12.00 per cent; Phosphate of Magnesia, 1.83 per cent; Soluble Salts, 0.70 per cent, or mineral matter, 68.90 per cent. While they contain Cartilage, 27.99 per cent; Fat, etc., 3.11 per cent, or animal matter 31.10 per cent.

In bone tissue there are two modifications of texture, the compact and the cancellated. The former—hard, dense, and ivory-like, is always situated externally; the latter porous and spongy lies within.