When a piece of bone is removed from an animal by an aseptic operation and is immediately buried in the tissues of the animal, new bone formation takes place in it. All authorities agree on this point. Does the transplanted bone die, and simply by its presence stimulate the surrounding tissues to form new bone in it, or, after the manner of a graft from a tree, does it survive, and itself form the new bone? This apparently simple question has been the occasion for a great amount of investigation, but has not yet been definitely answered. The weight of experimental evidence is on the side of the first hypothesis; circumstantial evidence is on the side of the second, and considerable experimental evidence also.
There are two main difficulties in our way: 1. It is not always possible to distinguish dead bone from living. 2. We are uncertain of our