SUMMARY. The bone graft is a trustworthy surgical agent, as proved by my uniform success, in its use in over 350 surgical cases. Also by a careful study microscopically, macroscopically, and by the Roentgen rays of its results, when used experimentally, both in the presence of primary union and sepsis. The cortical graft's field of usefulness is distinctly enhanced because of its resistance to tubercular and attenuated pyogenic infection.Its field is also enlarged by the use of the author's motor-driven instruments, circular saws of different sizes, the adjustable twin saws, and the lathe or dowel instrument with different adjustments for making various sizes of bone graft inlays, nails, or spikes as they are needed.By the use of this motor outfit and its products in conjunction with kangaroo tendon I have been able to avoid entirely the use of all metal in the form of screws, nails, Lane's plates, wire, etc., for internal bone-fixation purposes during the past two years. This has been made possible, largely, by making the best of well-known fundamental mechanical devices hitherto rarely, if at all, used in surgery, such as bone inlays, wedges, dowels, tongue and groove joints, mortised and dove-tail joints.