Abstract: To reduce damage to surrounding tissue while fragmenting some tissue such as for example not damaging the capsular wall while removing the lens during cataract removal surgery or not damaging artery or vein walls during bypass surgery while freeing the artery or vein to be transplanted, an incision is made for the insertion of surface--discriminating, rotating, fragmenting handpiece. The surface--discriminating fragmenting handpiece fragments and permits aspiration of the tissue without damaging the surrounding wall by fragmenting surfaces of higher inertia material but moving at a rate of speed and having openings between them of such a size that the more integrated lower mass, more flexible and smoother tissue is moved away from the fragmenting zone and the higher mass, lower flexibility or rougher tissue is fragmented.