Abstract: A plastic bone used as a training device or teaching aid for a surgeon for mechanically connecting bone fractures, comprising a plastic molded part, the size and dimension of which approximates that of a human extremity-shaft bone having an internal hollow compartment or cavity which extends past a marrow cavity region at the center of the shaft towards both shaft ends into the region of the spongy structured bone lacunae (spongiosa) and widens. The wall structure of the bone approximately corresponds to the solid or compact wall parts (compacta) of the natural structure in weight, strength and mechanical workability.